Research Repository :: Browsing by Author "Hosea, Ken M."

Browsing by Author "Hosea, Ken M."

Now showing 1 - 20 of 29

Bioactivity of Crude Extracts of Ascomycetes Isolated from Tanzanian Traditionally Fermented Milk, Mtindi
(2014-01) Mlimbila, Jane; Muruke, Masoud H.; Hosea, Ken M.
In an attempt to find potential functional foods in Tanzania, a study was conducted to assess bioactivity of 18 ethyl acetate extracts from nine (9) Ascomycetes strains. Namely; Candida tropicalis, C. pararugosa, Clavispora lusitaniae, Issatchenkia orientalis, Pichia kudriavzevii, Pichia guilliermondii, Galactomyces geotricum, Debaryomyces hansenii and Yarrowia lipolytica isolated from traditional fermented milk “mtindi”. Lethality test of the extracts was determined using Artemia salina naupalii in a Brine Shrimp Test (BST). The lethal concentration (LC50) obtained ranged from 89.7µg/ml to over 1000 µg/ml. Bioactivity results showed that, one of the 18 extracts had exhibited a strong antibacterial activity against Staphylococcus aureus, Pseudomonas aureginosa and Vibrio cholera having minimum inhibitory concentration (MIC) values of 0.1653mg/ml on each account. More than 40% of extracts exhibited strong to moderate antifungal activity against Cryptococcus neoformans (MIC 0.16 mg/ml – 1.25 mg/ml). In conclusion, these results suggest that yeasts found in traditional fermented milk have potential biological activity that could be used for treatment of some diarrhoeal and fungal infections and possibly tuberculosis.
Change in Composition of the Anopheles Gambiae Complex and Its Possible Implications for the Transmission of Malaria and Lymphatic Filariasis in North-Eastern Tanzania
(BioMed Central, 2012) Derua, Yahya A.; Alifrangis, Michael; Hosea, Ken M.; Meyrowitsch, Dan W.; Magesa, Stephen M.; Pedersen, Erling M.; Simonsen, Paul E.
A dramatic decline in the incidence of malaria due to Plasmodium falciparum infection in coastal East Africa has recently been reported to be paralleled (or even preceded) by an equally dramatic decline in malaria vector density, despite absence of organized vector control. As part of investigations into possible causes for the change in vector population density, the present study analysed the Anopheles gambiae s.l. sibling species composition in north-eastern Tanzania. The study was in two parts. The first compared current species complex composition in freshly caught An. gambiae s.l. complex from three villages to the composition reported from previous studies carried out 2-4 decades ago in the same villages. The second took advantage of a sample of archived dried An. gambiae s.l. complex specimens collected regularly from a fourth study village since 2005. Both fresh and archived dried specimens were identified to sibling species of the An. gambiae s.l. complex by PCR. The same specimens were moreover examined for Plasmodium falciparum and Wuchereria bancrofti infection by PCR. As in earlier studies, An. gambiae s.s., Anopheles merus and Anopheles arabiensis were identified as sibling species found in the area. However, both study parts indicated a marked change in sibling species composition over time. From being by far the most abundant in the past An. gambiae s.s. was now the most rare, whereas An. arabiensis had changed from being the most rare to the most common. P. falciparum infection was rarely detected in the examined specimens (and only in An. arabiensis) whereas W. bancrofti infection was prevalent and detected in all three sibling species. The study indicates that a major shift in An. gambiae s.l. sibling species composition has taken place in the study area in recent years. Combined with the earlier reported decline in overall malaria vector density, the study suggests that this decline has been most marked for An. gambiae s.s., and least for An. arabiensis, leading to current predominance of the latter. Due to differences in biology and vectorial capacity of the An. gambiae s.l. complex the change in sibling species composition will have important implications for the epidemiology and control of malaria and lymphatic filariasis in the study area.
Combined Production of Bioethanol and Biogas from Peels of Wild Cassava Manihot Glaziovii
(Elsevier, 2015) Moshi, Anselm P.; Temu, Stella G.; Ngesa, Ivo A.; Malmo, Gashaw; Hosea, Ken M.; Elisante, Emrode; Mattiasson, Bo
Cassava peels were pre-treated with alkali, enzyme and in sequential combination of alkali and enzyme, and used for production of bioethanol or biogas, or both (in sequence, bioethanol followed by biogas). The Biogas Endeavour and Automatic Methane Potential Test Systems were used for production of bioethanol and biogas, respectively. The bioethanol yield and volumetric productivity achieved with alkali pre-treatment combined in sequence with enzyme pre-treatment were 1.9 mol/mol and 1.3 g/L/h which was higher than the yield (1.6 mol/mol) and volumetric productivity (0.5 g/L/h) obtained from only enzyme pre-treated peels. Alkali combined in sequence with enzyme was proven to be the best treatment showing a 56% improvement in methane yield compared to the yield from untreated sample. Combined ethanol and methane production resulted in 1.2–1.3-fold fuel energy yield compared to only methane and 3–4-fold compared to only ethanol production. This study therefore provides practical data on the scenario best suited for the harnessing of energy from cassava peels.
Cytosolic Enzymes with a Mitochondrial Ancestry from the Anaerobic Chytrid Piromyces Sp. E2. Mol Microbiol 30:1017-1027
(1998) Akhmanova, Anna; Voncken, Frank; Harhangi, Harry R.; Hosea, Ken M.; Vogels, Godfried D.; Hackstein, Johannes H. P.
The anaerobic chytrid Piromyces sp. E2 lacks mitochondria, but contains hydrogen-producing organelles, the hydrogenosomes. We are interested in how the adaptation to anaerobiosis influenced enzyme compartmentalization in this organism. Random sequencing of a cDNA library from Piromyces sp. E2 resulted in the isolation of cDNAs encoding malate dehydrogenase, aconitase and acetohydroxyacid reductoisomerase. Phylogenetic analysis of the deduced amino acid sequences revealed that they are closely related to their mitochondrial homologues from aerobic eukaryotes. However, the deduced sequences lack N-terminal extensions, which function as mitochondrial leader sequences in the corresponding mitochondrial enzymes from aerobic eukaryotes. Subcellular fractionation and enzyme assays confirmed that the corresponding enzymes are located in the cytosol. As anaerobic chytrids evolved from aerobic, mitochondria-bearing ancestors, we suggest that, in the course of the adaptation from an aerobic to an anaerobic lifestyle, mitochondrial enzymes were retargeted to the cytosol with the concomitant loss of their N-terminal leader sequences.
Evaluation of Regeneration Potentials of Farmerpreferred Cassava (Manihot Esculenta Crantz) Landraces to Unlock Cassava Transformation Barriers
(2014) Elibariki, Gladness; Lupembe, M.; Hosea, Ken M.; Ndunguru, Joseph
Evaluation of cassava germplasms for in vitro regeneration ability is crucial for stable genetic improvement of this crop via genetic transformation systems. Methods for reliable and efficient transformation including somatic embryo regeneration and recovery of transgenic plants still need to be developed and customized for each cassava genotype. Twenty one Tanzanian farmer- preferred cassava (Manihot esculenta Crantz) landraces widely grown in major cassava growing zones were evaluated for somatic embryo induction, recovery, sustainability and plantlets regeneration to whole plants. Somatic embryogenesis was induced from cassava leaf lobes on Murashige and Skoog media supplemented with different concentrations of sucrose, Copper sulphate and 2, 4-Dichlorophenoxyacetic acid and further developed to plantlets. Frequency of somatic embryo production and subsequently regeneration stages were evaluated starting from 28 days post-inoculation. All cassava genotypes tested in this study were able to induce callus where by 62 % were able to induce somatic embryo cotyledons. Cassava landraces: Sagalato, Rangimbili, Mnazi and Kibandameno were highly responsive to somatic embryo production. The conversion rate of embryos into plantlets was variable depending on the cassava landrace, Sagalato being the most responsive and Kiroba the least. Somatic embryos from 8 cassava landraces reached plantlet stage, 5 of them being acclimatized and successfully developed to plants with normal phenotype and they rooted on soil. The regeneration potentials of farmer-preferred cassava landraces observed in this study is hoped to pave a way towards genetic improvement for both biotic and abiotic stresses via genetic engineering approaches.
Feasibility of Bioethanol Production from Tubers of Dioscorea Sansibarensis and Pyrenacantha Kaurabassana
(Elsevier, 2015) Moshi, Anselm P.; Nyandele, Jane P.; Ndossi, Humphrey P.; Sosovele, Eva M.; Hosea, Ken M.
Inedible tubers from Dioscorea sansibarensis (DS) and Pyrenacantha kaurabassana (PK) were found to be suitable feedstock for bioethanol production. Important composition parameters for bioethanol production for DS and PK are dry matter (% fresh tubers) ca. 20 and 6, total carbohydrates % dry weight base (db) ca. 68 and 47 and total protein (% db) ca. 16 and 10, respectively. DS and PK were found to contain inulin and galactomannan as principal polysaccharides (% of total carbohydrate) ca. 90 and 70, respectively. Diluted acid hydrolysis yielded ca. 100% of total reducing sugars. Ethanol yield ca. 56 and 35 g/L was obtained at high efficiency through batch fermentation of acid hydrolysate (25% w/v) of DS and PK, respectively. A simple technique of recording and monitoring ethanol through CO2 generated during fermentation correlated strongly with HPLC measurement R2 = 0.99. Thus, tubers from these plants are potential feedstocks for bioethanol production with no competing uses.
Free Radical Scavenging Activity of Some Fungi Indigenous to Tanzania
(2012) Masalu, Rose; Hosea, Ken M.; Malendeja, Sylives
The objective of this study was to evaluate free radical scavenging capacity of crude extracts from forest basidiomycetous fungi, domestic zygomycetous fungi and marine ascomycetous fungi. Lethal concentration values that kill 50% of the brine shrimps (LC50) were determined from 19 fungal extracts using brine shrimp test (BST). The LC50 values of fungal extract ranged between 0.28– 40µg/ml. The basidiomycetous (Lactarius volemoides) was the most toxic fungi with LC50 of 0.28µg/ml while ascomycete Pichia guilliermondii showed the least toxicity with LC50 of 40µg/ml. The concentrations of eleven fungal extracts were further evaluated on their ability to scavenge free radical using 1-diphenyl-2-picrylhydrazyl (α,α-diphenyl-β-picrylhydrazyl) (DPPH) as a dye reagent for spectrophotometric assay at 517nm. The extract concentrations that decreased the initial DPPH radical by 50% (EC50) were determined. The EC50 values ranged from 19–60.4µg/ml ascorbic acid equivalents. Extracts from an edible but undomesticated basidiomycetous fungus isolated from Miombo forest and identified as Termitomyces microcarpus showed the highest scavenging effect with EC50 at 19µg/ml while that from ascomycete Candida tropicalis showed the least EC50 at 60.4µg/ml. These results draw attention to wild undomesticated Miombo fungi as potential source of nutritional supplements worth further investigation.
Genetic Characterization of Osmotolerant Fermentative Saccharomyces Yeasts from Tanzania Suitable for Industrial Very High Gravity Fermentation
(2010) Sumari, Deborah; Hosea, Ken M.; Magingo, F. S. S.
Naturally occurring yeasts were sought from diverse Tanzanian environments and screened for industrial application. The yeasts were isolated from environments such as traditional brews and wines from various parts of Tanzania. In this regard, a total of thirty yeast isolates were screened for their suitability in Industrial Very High Gravity Fermentation (VHGF). Five of these isolates were able to grow and ferment medium with 40% initial sucrose concentration. Whereby, three were able to grow and ferment medium with 700 g/Litre (70% w/w) initial sucrose concentration. One of the three isolates coded LB2 isolated from a traditional Makonde sorghum brew was able to ferment a medium with initial sucrose concentration of 1000 g/Litre (100% w/w) at 30°C. On the basis of PCR-RFLP of the internal transcribed spacer (ITS) of the ribosomal DNA (rDNA), all the three most osmotolerant isolates were identified to belong to the Saccharomyces sensu stricto clade. Phylogenetic analysis of the 650 bp D1D2 domain of the large subunit 26S rDNA of the isolate LB2 clustered this isolate away from the so far known typical osmotolerant yeasts. The fermentation by LB2 isolate of 100% gravity substrate observed in this work is higher than any other encountered in the literatures reviewed.
Genetic Diversity and Identification of Duplicates in Selected Tanzanian Farmerpreferred Cassava Landraces Using Simple Sequence Repeat (SSR) Markers
(2013) Elibariki, Gladness; Njahira, Moses; Wanjala, Bramwel W.; Hosea, Ken M.; Ndunguru, Joseph
Genetic variation at twenty simple sequence repeat (SSR) markers loci was used to evaluate 21 Tanzanian farmerpreferred cassava landraces collected and maintained at Mikocheni Agricultural Research Institute laboratory in Tanzania.Two West African cassava genotypes and one Kenyan cassava were included in the clustering analysis. Genotyping with twenty high polymorphic SSR markers grouped the genotypes into three clusters derived from Neighbour joining analysis. Clustering analysis was well supported by principle component analysis (PCA). The first three axes of PCA with positive Eigen values accounted for 22.76, 15.93 and 8.48 % of the total variations respectively. No genotype duplicates were detected among the cassava landraces. Average gene diversity among the Tanzanian cassava was high (0.71) with an average heterozygozity of 0.46. Total number of alleles across all loci was 127 with mean number of alleles per locus being 6.35 and SSR markers had a mean polymorphic information content of 0.67. The results obtained in this study facilitated on selection of genotypes to include in the ongoing cassava genetic improvement programs in Tanzania and germplasm conservation.
Genetic Diversity of Plasmodium falciparum Strains in Children under Five Years of Age in Southeastern Tanzania
(2010) Sumari, Deborah; Hosea, Ken M.; Mugasa, Joseph P.; Abdulla, Salim
Strain diversity may play a role in delaying development of protective immunity in endemic areas. We evaluated genetic diversity of Plasmodium falciparum infected children before being treated with Sulphadoxine Pyrimethamine (SP) and Coartem™ in Southeastern Tanzania. Allelic diversity of P. falciparum strains were determined in order to further assist in correct estimation of recrudescent and new infections. P. falciparum isolated from 300 children aged 1-59 months was used in the study, where nested PCR followed by Restriction Fragment Length Polymorphism (RFLP) of highly polymorphic Merozoite surface protein 2 (msp2) was employed to understand the genetic diversity of the parasites population. Frequency of msp2 gene alleles was calculated and further associated with multiplicity of infection of children under five years of age. A total of 71 and 83 different msp2 alleles were found in Rufiji and Ulanga districts respectively. Children infected with either FC27 or 3D7 allelic type in Rufiji were 42% single, 55.3% double and 2.7% triple, while in Ulanga, 36.7% single, 62% double and 1.3% triple infections. Mean numbers of multiplicity of infections (MOI) in Rufiji and Ulanga were 1.6 and 1.3, respectively. These findings show a high genetic diversity of P. falciparum strains in study areas and low MOI could reflect production of susceptible parasites that immune response can accommodate or can be cleared by the drugs. Furthermore, 3D7 allelic type of msp2 gene was more prevalent than FC27 in Ulanga district, indicating association between msp2 allelic type and disease severity, hence predict possible vaccine candidate in the future.
High Bioethanol Titre from Manihot Glaziovii through Fed-Batch Simultaneous Saccharification and Fermentation in Automatic Gas Potential Test System
(Elsevier, 2014) Moshi, Anselm P.; Crespo, Carla F.; Badshah, Malik; Hosea, Ken M.; Mshandete, Anthony M.; Mattiasson, Bo
A process for the production of high bioethanol titre was established through fed-batch and simultaneous saccharification and fermentation (FB-SSF) of wild, non-edible cassava Manihot glaziovii. FB-SSF allowed fermentation of up to 390 g/L of starch-derived glucose achieving high bioethanol concentration of up to 190 g/L (24% v/v) with yields of around 94% of the theoretical value. The wild cassava M. glaziovii starch is hydrolysable with a low dosage of amylolytic enzymes (0.1–0.15% v/w, Termamyl® and AMG®). The Automatic Gas Potential Test System (AMPTS) was adapted to yeast ethanol fermentation and demonstrated to be an accurate, reliable and flexible device for studying the kinetics of yeast in SSF and FB-SSF. The bioethanol derived stoichiometrically from the CO2 registered in the AMPTS software correlated positively with samples analysed by HPLC (R2 = 0.99).
High Temperature Simultaneous Saccharification and Fermentation of Starch from Inedible Wild Cassava (Manihot Glaziovii) to Bioethanol Using Caloramator Boliviensis
(Elsevier, 2015) Moshi, Anselm P.; Hosea, Ken M.; Elisante, Emrode; Mamo, G.; Mattiasson, Bo
The thermoanaerobe, Caloramator boliviensis was used to ferment starch hydrolysate from inedible wild cassava to ethanol at 60 °C. A raw starch degrading α-amylase was used to hydrolyse the cassava starch. During fermentation, the organism released CO2 and H2 gases, and Gas Endeavour System was successfully used for monitoring and recording formation of these gaseous products. The bioethanol produced in stoichiometric amounts to CO2 was registered online in Gas Endeavour software and correlated strongly (R2 = 0.99) with values measured by HPLC. The organism was sensitive to cyanide that exists in cassava flour. However, after acclimatisation, it was able to grow and ferment cassava starch hydrolysate containing up to 0.2 ppm cyanide. The reactor hydrogen partial pressure had influence on the bioethanol production. In fed-batch fermentation by maintaining the hydrogen partial pressure around 590 Pa, the organism was able to ferment up to 76 g/L glucose and produced 33 g/L ethanol.
A Hydrogenosome with Pyruvate Formate-Lyase: Anaerobic Chytrid Fungi Use an Alternative Route for Pyruvate Catabolism. Mol Microbiol 32:1103-1114
(Wiley, 1999) Akhmanova, Anna; Voncken, Frank; Hosea, Ken M.; Harhangi, H.; Keltjens, J. T.; Op Den Camp, H. J.; Vogels, G. D.; Hackstein, Johannes H. P.
The chytrid fungi Piromyces sp. E2 and Neocallimastix sp. L2 are obligatory amitochondriate anaerobes that possesshydrogenosomes.Hydrogenosomes arehighly specialized organelles engaged in anaerobic carbon metabolism; they generate molecular hydrogen and ATP. Here, we show for the ®rst time that chytrid hydrogenosomes use pyruvate formate-lyase (PFL) and not pyruvate:ferredoxin oxidoreductase (PFO) for pyruvate catabolism, unlike all other hydrogenosomes studied to date. Chytrid PFLs are encoded by a multigene family and are abundantly expressed in Piromyces sp. E2 and Neocallimastix sp. L2. Western blotting after cellular fractionation, proteinase K protection assays and determinations of enzyme activities reveal that PFL is present in the hydrogenosomes of Piromyces sp. E2. The main route of the hydrogenosomal carbon metabolism involves PFL; the formation of equimolar amounts of formate and acetate by isolated hydrogenosomes excludes a signi®cant contribution by PFO. Our data support the assumption that chytrid hydrogenosomes are unique and argue for a polyphyletic origin of these organelles.
In Vitro Antimicrobial Assay Of Plants Used In Traditional Medicine In Bukoba Rural District, Tanzania
(2007) Kisangau, Daniel P.; Hosea, Ken M.; Joseph, Cosam C.; Lyaruu, Herbert V. M.
Plants used in traditional medicine in Bukoba Rural district in Tanzania were evaluated for their in vitro antimicrobial activities. Plant materials from eight plant species (Harungana madagascariensis (Lam) Poir., Jatropha curcas L., Lantana trifolia L., Plectranthus barbatus Andr., Pseudospondias microcarpa Engl., Psorospermum febrifugum Spach, Teclea nobilis Del. and Vernonia adoensis [Warp.] SL) were collected based on ethnomedical information provided by traditional herbal practitioners. Results of the study indicate that extracts from the eight plant species were active against at least one or more of the test organisms (Bacillus subtilis, Staphylococcus aureus [gram positive], Escherichia coli, Pseudomonas aeruginosa [gram negative] and Candida albicans [Yeast]). A profile of secondary metabolites (alkaloids, terpenoids, triterpenes, phenolics, tannins, flavonoids, anthraquinones, flavonols/flavones and /or chalcones, sterols and saponins) was obtained for three plant species (Jatropha curcas L., Plectranthus barbatus Andr., and Pseudospondias microcarpa Engl.). The paper discusses the probable therapeutic basis of these traditional plants based on their secondary metabolite profiles and for the first time draws research attention to Bukoba Rural district as a source for plants with potential pharmaceutical applications.
In Vitro Cytotoxicity of Some Medicinal Plants Used in Traditional Medicine in Tanzania
(2011) Kisangau, Daniel P.; Lyaruu, Herbert V. M.; Hosea, Ken M.; Joseph, C. C.; Bruno, L. N.; Devkota, Krishna P.; Bogner, T.; Sewald, Norbert
Plants used in traditional medicine in Tanzania were screened for their cytotoxicity using the brine shrimp and CellTiter-BlueTM cell viability assays. Dichloromethane extracts of Capparis erythrocarpos, Cussonia arborea, Dracaena steudneri, Lannea schimperi, Pseudospondias microcarpa, Rauvolfia vomitoria, Sapium ellipticum and Zehneria scabra exhibited various cytotoxic activities against brine shrimp larvae. Only semi-purified fractions of C. erythrocarpos, C. arborea, D. steudneri, Lannea schimperi and S. ellipticum and one pure compound Lup-20(29)-en-3-one (1) from S.ellipticum were tested against K562 Leukaemia cell line using the CellTiter-BlueTM cell viability assay method. In the brine shrimp lethality assay, P. microcarpa was the most toxic plant with an LC50 value of 1.9 μg/ml (95%CI, 1.6-2.2 μg/ml) , while Z. scabra was the least toxic plant with LC50 value of 179.4 μg/ml (95%CI, 156.1-213.9 μg/ml). In the CellTiter-BlueTM cell viability assay, the mean % cell vitality growth for the fractions of each of the five plant species C. arborea, C. erythrocarpos, D. steudneri, L. schimperi and S. ellipticum were 43.1%, 67.2%, 82.1%, 52.3% and 87.6% respectively, with P<0.0001 and 95% confidence intervals (CI) of 54.746-81.082 μg/ml. The IC50 concentration for compound Lup-20(29)-en-3-one (1) was 1.747x10-6 μM with 95% confidence intervals (CI) of 3.019x10-7 to 1.011x10-4 μM. Results indicate that most of the extracts tested were relatively non-toxic hence supporting the inherent use of these plants in traditional medicine.
Induction of Early Apoptosis and Reactive Oxygen Species (ROS) Production by Tanzanian Basidiomycete ( Cantharellus Miomboensis )
(2010) Masalu, Rose; Hosea, Ken M.; Meyer, Mervin; Lyantagaye, Sylvester L.; Kanyande, Stonard
Cantharellus miomboensis is a new basidiomycete fungus recently found in Miombo woodlands in Tanzania. In this study, crude extract was prepared from fruiting bodies of C. miomboensis and was in vitro screened for its cytotoxicity using Tetrazolium salt (3-(4,5-dimethlthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) in human cell lines namely; Hepatocellular carcinoma (HepG2), Human non-small cell lung carcinoma (H157) and Human colon adenocarcinoma (HT.29). Thereafter, pro-apoptotic effects were determined using biochemical changes in apoptotic cells. These included externalization of phospholipid phosphatidylserine (PS) using APO Percentage dye by flow cytometry and depolarization of mitochondrial membrane potential using Tetramethyl rhodamine ethyl ester perchlorate (TMRE) assay. The test extract was found to induce dose dependent PS externalization on human cell lines when treated with various concentrations (1 - 5 mg/ml) and completely depolarized the mitochondrial membrane potential after 6 hours on HepG2 cell line. When the extract was examined for ROS production using 2’,7’- dichlorofluorescin diacetate (DCFH-DA) staining, there was no ROS generation found in HepG2 cells. It is therefore concluded that C. miomboensis extract is able to induce apoptosis in HepG2 cells and PS externalization and loss of mitochondrial membrane potential in HepG2 cells appear to be independent of ROS production.
Molecular Identification and Proteinase Activity of Yeasts Isolated from Fermented Milk
(2013) Mlimbila, Jane; Hosea, Ken M.; Muruke, Masoud H.
The aim of this study was to identify yeasts from traditional Tanzanian fermented milk, “mtindi” and industrial fermented milk, “yoghurt” and to determine their in vitro proteolytic activities. A total of twenty five yeast isolates were studied. Identification was done by ribosomal DNA - Polymerase Chain Reaction (PCR) amplification and sequencing of the domains D1/D2 of the 26S rRNA gene. The identified yeasts were Candida tropicalis, C. pararugosa, Clavispora lusitaniae, Issatchenkia orientalis/Pichia kudriavzevii, Pichia guilliermondii/Meyerozyma guilliermondii, Galactomyces geotricum, Debaryomyces sp and Yarrowia lipolytica. However, Y. lipolytica and D. hansenii were detected from yoghurt samples only, while G. geotrichum was found in both mtindi and yoghurt samples. Candida sp. and Pichia sp. were detected in mtindi samples only. The highest yeast load was of C. paragurosa (over log 6 CFU/ml) and P. guilliermondii was the least isolated strain in numbers of slightly over log 2CFU/ml (p<0001). Proteolytic activity was analysed by plate assay using nutrient agar media supplemented with milk casein. Over 80% of the isolates were protease positive. The highest activity was detected on C. pararugosa isolated from mtindi with the diameter of clear zone 36.667+5.4mm, (p<0.01). Our results showed the potential of dairy yeasts as a source for further exploitation of the production of proteolytic substances with either potential health benefits or spoilage abilities.
New antimicrobial, mosquito larvicidal and other metabolites from two Artabotrys species
(Taylor & Francis, 2012-09) Nyandoro, Stephen S.; Joseph, Cosam C.; Nkunya, Mayunga H. H.; Hosea, Ken M.
Azabicycloheptenoylditerpene 1-((2E,6E,10E)-3,7,11,15-tetramethylhexadeca-2,6,10,14-tetraenyl)-2-azabicyclo[2.2.1]hept-5-en-3-one (artamodamide, 1), diphenylpentanoid (E)-1,5-bis(4-hydroxyphenyl)-pent-1-en-3-one (artamenone, 2) and N-methoxy-5-oxoaporphinoid (artamonteirine, 3) were isolated as new metabolites from Artabotrys modestus Diels ssp macranthus Verdc. and Artabotrys monteiroae Oliv. (Annonaceae), together with several known compounds. Structures of the isolated compounds were established based on analysis of their spectroscopic data. Some of the compounds exhibited antimicrobial activity (minimum inhibitory concentration values between 2.5 and 20 µg mL−1) and varying levels of mosquito larvicidal potency. These results further indicate the versatility of the family Annonaceae in accumulating bioactive natural products with diverse chemical structures and wide spectra of biological activities, and hence suggesting the need to conserve Annonaceae species that are potentially vulnerable to extinction.
New Antimicrobial, Mosquito Larvicidal and Other Metabolites from Two Artabotrys Species
(Taylor & Francis, 2013) Nyandoro, Stephen S.; Joseph, Cosam C.; Nkunya, Mayunga H. H.; Hosea, Ken M.
Azabicycloheptenoylditerpene 1-((2E,6E,10E)-3,7,11,15-tetramethylhexadeca-2,6,10,14-tetraenyl)-2-azabicyclo[2.2.1]hept-5-en-3-one (artamodamide, 1), diphenylpentanoid (E)-1,5-bis(4-hydroxyphenyl)-pent-1-en-3-one (artamenone, 2) and N-methoxy-5-oxoaporphinoid (artamonteirine, 3) were isolated as new metabolites from Artabotrys modestus Diels ssp macranthus Verdc. and Artabotrys monteiroae Oliv. (Annonaceae), together with several known compounds. Structures of the isolated compounds were established based on analysis of their spectroscopic data. Some of the compounds exhibited antimicrobial activity (minimum inhibitory concentration values between 2.5 and 20 µg mL−1) and varying levels of mosquito larvicidal potency. These results further indicate the versatility of the family Annonaceae in accumulating bioactive natural products with diverse chemical structures and wide spectra of biological activities, and hence suggesting the need to conserve Annonaceae species that are potentially vulnerable to extinction.
Production of Bioethanol from Wild Cassava Manihot glaziovii through Various Combinations of Hydrolysis and Fermentation in Stirred Tank Bioreactors
(2015) Moshi, Anselm P.; Hosea, Ken M.; Elisante, Emrode; Mshandete, Anthony M.; Nges, Ivo A.
Aim of the Study: The aim of this study was to evaluate three ethanol fermentation approaches namely (I) separate hydrolysis and common fermentation (II) separate hydrolysis and fermentation and (III) simultaneous saccharification and fermentation in stirred tank reactors using inedible wild cassava as feedstock. Study Design: Tubers of wild cassava (Manihot glaziovii) were obtained from two districts i Tanzania. Fermentation of hydrolysate and partially liquefied cassava flour was performed in stirred tank reactors. Methodology: Feedstock composition analysis for structural carbohydrate was performed using acid hydrolysis and high pressure liquid chromatography technique. Analysis of total nitrogen was done by Kjeldahl acid digestion technique, total cyanide was determined using linamarase loaded picrate paper whereas macro-and micronutrients were analysed by inductively coupled plasma atomic emission spectrometry. Thermostable α-amylase and glucoamylase were used to partially hydrolyze the cassava flour to fermentable sugars prior to yeast fermentation. The hydrolysis (liquefaction) was performed at 90°C, 1h followed by saccharification using glucoamylase at 60°C, 2h for approaches I and II. For approach III, liquefaction was performed at 90°C, 1h followed by direct saccharification and fermentation. Fermentation of hydrolysate and partially liquefied starch from wild cassava was done in stirred tank reactors at 30±2°C using baker’s yeast. Place and Duration of Study: Department of Biotechnology, Lund University from January to June 2014. Results: The wild cassava (M. glaziovii) tubers possessed comparable physical dimensions to the domesticated cassava, however they displayed higher average flesh proportion (76 to 79%) compared to the domesticated cassava (74%). Compositional analysis disclosed that the wild cassava possessed interesting properties for bioethanol production such as dry matter of up to 89% w/w, degradable carbohydrate up to 90% (dry weight basis), total kjeldahal nitrogen 0.8-1.6% w/w and satisfactory concentration of macro-and micronutrients. Amongst the three fermentation approaches, high ethanol titre of 10-11% (v/v) at high conversion efficiency of 97.6% was achieved for separate hydrolysis and fermentation and simultaneous saccharification and fermentation, whereas low ethanol titre (4.2% v/v) at efficiency of 39% was achieved for separate hydrolysis and common fermentation. Volumetric productivities for the three approaches; ‘separate hydrolysis and common fermentation’, ‘separate hydrolysis and fermentation’, and ‘simultaneous saccharification and fermentation’ were 2.0, 5.5 and 6.5 respectively. Conclusion: The results obtained in the present study demonstrated that wild cassava has a high starch content, contain balanced nutrients required for efficient bioethanol production and that simultaneous saccharification and fermentation is the best approach for bioconversion of the wild cassava to bioethanol using stirred tank reactors.

Browsing by Author "Hosea, Ken M."

Results Per Page

Sort Options