Optimisation of alpha-amylase inhibitor production in solid state fermentation.

Though not a known producer of alpha-amylase inhibitor, the potential of Streptomyces xinghaiensis AAI-2 to produce this important metabolite was assessed and the process optimised in solid substrate using response surface methodology. The isolate was grown in an inoculum medium, inoculated into wheat bran and supplemented with a basal medium for production of alpha amylase inhibitor. Optimum conditions were determined by Response Surface Methodology. The extract was recovered using sodium phosphate buffer at refrigerated temperature and assay for the presence of alpha-amylase inhibitor was carried out by Dinitrosalicylic acid method. Based on the results of the experimental trials and iteration with those values, it was predicted that optimal pH for alpha-amylase inhibitor production using S. xinghaiensis in solid culture of wheat bran was pH 6.4-6.9 while optimal moisture content and incubation time were predicted as 71%-73% and 9-12 days respectively.

Assessment of microbiological quality of sachet-packaged drinking water in Western Nigeria and its public health significance.

OBJECTIVE: To assess the microbiological quality of sachet-packaged drinking water in Western Nigeria and its impact on public health. STUDY DESIGN: Cross-sectional microbiological testing. METHODS: Ninety-two sachet-packaged water samples were analysed for microbiological and metal qualities. Total bacterial and coliform counts were determined, and the presence of Escherichia coli, an important water quality indicator, was tested. The level of conformity of the water processors with the guidelines of Nigeria's quality regulatory agency was also determined. RESULTS: Varying levels of microbial contamination were recorded in samples from the different sampling locations. The total bacteria count ranged between 2.86 and 3.45log colony-forming units (cfu)/ml. The highest coliform count recorded was 1.62log cfu/ml. Faecal coliform E. coli was detected in one sample from Oke-Iho and one sample from Okaka, representing 2.2% of total samples. Lead and manganese were not found in any of the samples. However, iron was detected and the highest iron concentration (0.10mg/l) was detected in samples from Ikorodu. The bacteria that were identified from the water samples included E. coli, Pseudomonas aeruginosa, Enterobacter aerogenes, Klebsiella sp., Proteus vulgaris, Alcaligenes faecalis, Bacillus cereus, Staphylococcus aureus, Streptococcus lactis, Aeromonas sp. and Micrococcus luteum. Many of the water processors did not comply with the guidelines of the quality regulatory agency. CONCLUSIONS: Some of the sachet-packaged samples of drinking water were of poor quality. The results indicate a need for Nigeria's quality regulatory agency to take appropriate measures in safeguarding public health.

Antagonistic activity of bacteriocin produced by Lactobacillus species from ogi, an indigenous fermented food.

Seven Lactobacillus species each with one or more strains were isolated from various fermented cereal gruel's (ogi). They were identified as L. plantarum (3 strains), L. delbrueckii (1 strain), L. brevis (2 strains), L. reuteri (2 strains), L. casei (1 strain), L. fermentum (1 strain) and L. acidophilus (1 strain). Bacteriocin production was observed in cell-free supernatants of 8 of these strains with L. fermentum, L. delbrueckii and L. reuteri strains (white maize ogi) being negative. The bacteriocin produced by the eight strains inhibited the growth of various target organisms with the inhibition strongly noticed using Enterococcus faecalis as indicator. While catalase treatment, pH changes and heat treatment up to 80 degrees C had no effect on the activity of bacteriocin from these isolates, treatment with trypsin and proteinase K resulted in complete loss of inhibitory activity of the bacteriocins. A reduction in the inhibitory activity of the bacteriocins was also found to occur with increasing concentrations of glucose or peptone in the cultivation medium.

Effect of process improvement on the physico-chemical properties of infant weaning food from fermented composite blends of cereal and soybeans.

Saccharomyces cerevisiae and Lactobacillus plantarum ATCC 10776 were used as starters to ferment various composite blends of cereals and legumes produced through malting and toasting of two varieties of maize--Zea mays (DMR-LSR white & DMR-ESR yellow), sorghum--Sorghum bicolor (Dawa white & Dawa red) and one variety of soybeans (Glycine ax). Compared to the untoasted and unmalted fermented blends, a relatively lower pH (3.6), highly sour product was obtained with 12 h of fermentation. Results also showed that cereal and soybean toasting brought about a better reconstitution indices (B25, 84 ml; B45, 87 ml), water holding capacities (B25, 0.68 ml/g; B45, 0.62 ml/g), bulk densities (C15, 11.6; C35, 10.8) and gross energy (B15, 501.5 k cal/100g; B45, 508.5 kcal/100g) at the end of fermentation. Furthermore, reductions in total polyphenol and tannin contents were observed with fermentation of toasted and malted cereal blends supplemented with toasted and malted soybeans while porridges from the same blends displayed desirable starch stability and consistent gelling tendency, although B15 (a ferment of malted, toasted white maize supplemented with toasted and malted soybean) fell within acceptable limits. In all, the physical characteristics were affected by varieties of cereal and soybeans.

Effect of bacterial galactosidase treatment on the nutritional status of soybean seeds and its milk derivative.

Four field strains of Lactobacillus plantarum (LS 4, 19, 21, 133) obtained from fufu (a semi-solid product obtained by boiling fermented cassava--Manihot esculenta Crantz) and a type strain DSM 2017 were grown on different carbon sources to induce galactosidase production. LS 21 produced the highest concentration of alpha- and beta-galactosidase with 0.28 mumol/l and 0.28 mumol/l respectively on lactose and galactose. Milk obtained from soybean seeds treated with the enzyme mixture for 24 h showed a 99, 98 and 96% reduction respectively in the raffinose, stachyose and sucrose content when compared with the dry soybean seed. Glucose and galactose which were not detected in the dry seeds became readily available after soaking in both enzyme mixture and distilled water. Although there was reduction in the nutritional composition of both milk samples, reduction of phytic acid and trypsin inhibitor is beneficial to the consumers. The result of the sensory evaluation showed that the milk prepared from enzyme-treated soybean seeds was rated better in terms of flavour, texture, appearance and palatability.

Effect of cassavar cultivar, age and pretreatment processes of cellulase and xylanase production from cassava waste by Trichoderma harzianum.

Cassava wastes--the peel and the root fibre were taken through various pretreatment procedures before being subjected to solid state fermentation with Trichoderma harzianum. Most of the pretreatment processes increased the cellulose and hemicellulose content of the cassava peel and fibre by as high as 155% while sulfuric acid treatment resulted in 25.3% loss in the peel hemicellulose. The best pretreatment found to be 1% NaOH at 120 degrees C gave the highest production of the Cx, the Cl and xylanase enzymes with the cassava root fibre. Xylanase and cellulase production with the exception of the Cx was found to be affected by age while an improved cassava variety TMS(2) 1425 peel and fibre rated highest in terms of production of the enzymes. Percentage hydrolysis within range of 56.52-67.64% were recorded for the enzymes on sorghum grains.