Browsing by Author "Ojwang D. Otieno"

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    Genetic Diversity of Kenyan Native Oyster Mushroom (Pleurotus)
    (Taylor & Francis Online, 2017-01-20) Ojwang D. Otieno; Calvin Onyango; Justus Mungare Onguso; Lexa G. Matasyoh; Bramwel W. Wanjala; Mark Wamalwa; Jagger J.W. Harvey
    Members of the genus Pleurotus, also commonly known as oyster mushroom, are well known for their socioeconomic and biotechnological potentials. Despite being one of the most important edible fungi, the scarce information about the genetic diversity of the species in natural populations has limited their sustainable utilization. A total of 71 isolates of Pleurotus species were collected from three natural populations: 25 isolates were obtained from Kakamega forest, 34 isolates from Arabuko Sokoke forest and 12 isolates from Mount Kenya forest. Amplified fragment length polymorphism (AFLP) was applied to thirteen isolates of locally grown Pleurotus species obtained from laboratory samples using five primer pair combinations. AFLP markers and internal transcribed spacer (ITS) sequences of the ribosomal DNA were used to estimate the genetic diversity and evaluate phylogenetic relationships, respectively, among and within populations. The five primer pair combinations generated 293 polymorphic loci across the 84 isolates. The mean genetic diversity among the populations was 0.25 with the population from Arabuko Sokoke having higher (0.27) diversity estimates compared to Mount Kenya population (0.24). Diversity between the isolates from the natural population (0.25) and commercial cultivars (0.24) did not differ significantly. However, diversity was greater within (89%; P > 0.001) populations than among populations. Homology search analysis against the GenBank database using 16 rDNA ITS sequences randomly selected from the two clades of AFLP dendrogram revealed three mushroom species: P. djamor, P. floridanus and P. sapidus; the three mushrooms form part of the diversity of Pleurotus species in Kenya. The broad diversity within the Kenyan Pleurotus species suggests the possibility of obtaining native strains suitable for commercial cultivation.
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    Quality Evaluation of Oil from Seeds of Wild Plant Tylosema fassoglensis in Kenya
    (Journal of Food Processing, 2015-07-15) Ojwang D. Otieno; Okewo B. Awuor; Wanjala G. Wafula
    Tylosema fassoglensis is a plant species that is native to Sub-Saharan Africa. The aim of this study was to evaluate the physicochemical properties of oil from T. fassoglensis in Kenya. Seeds of T. fassoglensis were collected from Mombasa, Taita Taveta, Homa Bay, and Siaya regions. Counts of T. fassoglensis in each region were recorded during the entire survey period. The highest distribution was recorded in Homa Bay followed by Siaya region. Distribution was the least in Taita Taveta and Mombasa regions. The analysis of the physicochemical characteristics of the oil was performed according to the official methods of analysis and the recommended practices of the American Oil Chemists Society. Oil content of 36.4% was obtained. The oil had refractive index 1.47 at 40°C, peroxide value 6.34 meq O2/kg, iodine value 94.06 g of I2/100 g, saponification value 145.93 mg KOH/g of oil, acid value 2.49 ± 0.56 mg KOH/g of oil, and unsaponifiable matter 5.87 g/kg. The oil had Lovibond color index of 2.0Y+28.0R. Oil content of T. fassoglensis is comparable with those of most oil crop under commercial production. The physicochemical properties of oil from T. fassoglensis are within the range recommended by FAO/WHO and hence suitable for human consumption.
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    Strategies for Improving Hydrolytic Efficiency of Crude Multienzyme Extracts in Mushroom Processing
    (Elsevier Inc, 2022-11) Ojwang D. Otieno; Mulaa F. Jakim; Obiero George; Midiwo Jacob
    The current study investigated and optimized key process parameters affecting mushroom hydrolysis with crude enzymatic extract. The crude enzyme was prepared by solid-state fermentation of pineapple peels using Aspergillus niger. The reaction parameters viz. time, temperature, pH and enzyme concentration were optimized using the central composite design of the response surface methodology. The model predicted glucose yield of 1.49 mg/mL at optimal pH of 6.5, temperature of 50 °C, enzyme loading of 5 % (v/v), and reaction time of 12 h. Mushroom hydrolysis at the same optimal model conditions, increased glucose yield by 10%. More so supplementing SSF media with 0.2% (w/v) Tween-80 and 0.08% (w/v) yeast extract at moisture level of 70–75% significantly (p value < 0.05) improved hydrolytic efficiency of the crude enzyme extract by 2.2-fold. This study provides baseline data that will be useful in developing a low-cost enzyme-based process for hydrolyzing mushrooms to recover high-value products.
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    Utilization of fruit waste substrates in mushroom production and manipulation of chemical composition
    (Science Direct, 2020-01) Ojwang D. Otieno; Francis J. Mulaa; George Obiero; Jacob Midiwo
    The current study evaluated the effect of mushroom cultivation using fruit waste substrates on yield performance and antioxidant activities. The total phenolic content and the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities of the mushroom extracts were determined using colorimetric method. Mushroom P. eryngii had the highest yield of 87.2 ± 2.4 g/100 g dry substrate when grown on pineapple peels, while P.ostreatus yielded the least fruiting bodies 53.1 ± 1.8 g/100 g dry substrate when grown on orange peels. Similarly, P. eryngii grown on pineapple peels and P. ostreatus grown on orange peels had the highest and lowest biological efficiencies of 94.2 ± 3.5% and 69 ± 4.3%, respectively. The total phenolic content of P.ostreatus grown on avocado peels was 26.4 ± 3.8 mg GAE/g dry extract, while P.eryngii grown on avocado peels had the lowest at 9.3 ± 0.2 mg GAE/g dry extract. Mushrooms cultivated on fruit wastes generally exhibited higher DPPH activities than those grown on wheat straw (control) substrate. This study provided baseline information on the potential role of fruit waste substrates in mushroom growth and chemical composition.
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    Utilization of Fruit Waste Substrates in Mushroom Production and Manipulation of Chemical Composition
    (Elsevier B.V, 2022-01) Ojwang D. Otieno; Mulaa Francis J.; Obiero George; Midiwo Jacob
    The current study evaluated the effect of mushroom cultivation using fruit waste substrates on yield performance and antioxidant activities. The total phenolic content and the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities of the mushroom extracts were determined using colorimetric method. Mushroom P. eryngii had the highest yield of 87.2 ± 2.4 g/100 g dry substrate when grown on pineapple peels, while P.ostreatus yielded the least fruiting bodies 53.1 ± 1.8 g/100 g dry substrate when grown on orange peels. Similarly, P. eryngii grown on pineapple peels and P. ostreatus grown on orange peels had the highest and lowest biological efficiencies of 94.2 ± 3.5% and 69 ± 4.3%, respectively. The total phenolic content of P.ostreatus grown on avocado peels was 26.4 ± 3.8 mg GAE/g dry extract, while P.eryngii grown on avocado peels had the lowest at 9.3 ± 0.2 mg GAE/g dry extract. Mushrooms cultivated on fruit wastes generally exhibited higher DPPH activities than those grown on wheat straw (control) substrate. This study provided baseline information on the potential role of fruit waste substrates in mushroom growth and chemical composition.
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    Utilization of Fruit Waste Substrates in Mushroom Production and Manipulation of Chemical Composition
    (Elsevier B.V, 2022-01) Ojwang D. Otieno; Mulaa Francis J.; Obiero George; Midiwo Jacob
    The current study evaluated the effect of mushroom cultivation using fruit waste substrates on yield performance and antioxidant activities. The total phenolic content and the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities of the mushroom extracts were determined using colorimetric method. Mushroom P. eryngii had the highest yield of 87.2 ± 2.4 g/100 g dry substrate when grown on pineapple peels, while P.ostreatus yielded the least fruiting bodies 53.1 ± 1.8 g/100 g dry substrate when grown on orange peels. Similarly, P. eryngii grown on pineapple peels and P. ostreatus grown on orange peels had the highest and lowest biological efficiencies of 94.2 ± 3.5% and 69 ± 4.3%, respectively. The total phenolic content of P.ostreatus grown on avocado peels was 26.4 ± 3.8 mg GAE/g dry extract, while P.eryngii grown on avocado peels had the lowest at 9.3 ± 0.2 mg GAE/g dry extract. Mushrooms cultivated on fruit wastes generally exhibited higher DPPH activities than those grown on wheat straw (control) substrate. This study provided baseline information on the potential role of fruit waste substrates in mushroom growth and chemical composition.