RESUMO
Aims: Sclerotium rolfsii is a pathogen of agricultural crops such as tomatoes. Trichoderma viride has been shown to control this pathogen effectively but the optimum conditions of this biocontrol agent need to be determined. This piece of research was therefore aimed at studying the conditions that could be maintained in maximizing the full potential of T. viride. Methodology and results: Malt extract agar was separately supplemented with different carbon sources (glucose, sucrose, maltose, lactose, and mannitol), nitrogen sources (peptone, ammonium nitrate, zinc nitrate and sodium nitrate) as well as salts (NaCl, CaCl2, KI, BaCl2) at different concentrations. Effect of different temperature and pH ranges was also evaluated. All the carbon used supported the growth of both S. rolfsii and T. viride at all concentrations. The growth of S. rolfsii was less than 90 mm at 3% of all the carbon used compared to the plates in which no carbon sources were added whereas the growth of T. viride was 90 mm. There were morphological changes in the growth of both T. viride and S. rolfsii with increase in concentrations of peptone and ammonium nitrate. The greenish colour of T. viride was completely lost while S. rolfsii became fluffier. For peptone, the percentage reduction ranged from 68.52 to 63.33 while for zinc nitrate and sodium nitrate, the percentage reduction ranged from 85.19 to 80.74 and 55.00 to 43.70 respectively. Also, there was increase in antagonistic property of T. viride with the inclusion of salts (NaCl, CaCl2 and KI) at all concentrations used. However, barium chloride was toxic to T. viride at 2-5% (w/v). The optimum temperature and pH for the antagonistic property of T. viride appeared to be 37 °C and 6.0 respectively. Conclusion, significance and impact of study: Inclusion of different carbon, nitrogen and salts increased the antagonistic activities of T. viride against S. rolfsii although lactose appeared to be the best carbon source while zinc nitrate and CaCl2 were the best nitrogen and salt respectively. Barium chloride was toxic to T. viride at 2-5% (w/v).
RESUMO
Aim: This study investigated the effect of single cultures of Bacillus subtilis and B. pumilus on nutrient and anti-nutrient contents of ground-cooked Lima bean seeds. Methodology: Lima bean seeds were ground and fermented naturally as well as with single starters of B. subtilis and B. pumilus (previously isolated from naturally fermented Lima bean seeds) for nine days. Microbial analyses, pH, total titratable acidity and the temperature of the fermenting samples were carried out on daily basis, nutritional composition at two day intervals while the anti-nutrient contents were determined before and after the fermentation period. Results: Higher microbial counts were observed in starter fermented samples than the naturally fermented samples. The pH increased throughout the fermentation period with the highest in B. subtilis fermented sample but was not significantly higher (P<.05) than B. pumilus fermented sample while the total titratable acidity which however decreased mostly in B. subtilis was also not significantly different from B. pumilus fermented sample. Temperature increased up to the fifth day in both starter samples but higher in B. subtilis fermented substrate but up to seventh day in naturally fermented sample. Starter culture fermented samples had the highest moisture, fat and ash contents at the end of the fermentation while the protein values increased in all the samples with the highest in B. subtilis fermented sample (25.34%) while B. pumilus and naturally fermented sample contained 24.32% and 22.22% respectively. Oxalate, phytic acid and cyanide were more reduced in naturally fermented sample than the starter fermented samples while the highest reductions were observed in saponin and tannin contents of B. subtilis fermented sample. Organoleptic parameters were rated better in the Lima bean seeds fermented with starter cultures than the naturally fermented sample. Conclusion: This study revealed that Lima bean seeds fermented with single starter cultures of B. subtilis and B. pumilus enhanced the nutrient contents and organoleptic qualities of the products.