Production of a thermostable α-amylase from Bacillus sp. PS-7 by solid state fermentation and its synergistic use in the hydrolysis of malt starch for alcohol production

A solid state fermentation based bacterial α-amylase and fungal glucoamylase system and its suitability for the hydrolysis of wheat starch

In this study, mutation by UV-radiation and medium optimization were used to enhance production of citric acid through the screening of five local strains of Aspergillus niger using hydrolyzed cassava peel medium. Mutant strains were evaluated for citric acid production, and the physico-chemical parameters for citric acid production were further optimized using Central Composite Design (CCD) of Response Surface Methodology. Among the wild strains, a strain (FUO 2) gave highest citric acid yield of 1.93 g/l, while the mutant strain FUO 1 10 obtained after 10 min of exposure to UV-radiation yielded 9.4 g/l, an improvement of 4.87 fold. Process optimization using the mutant strain (FUO 1 10 ) on the input parameters of substrate concentration, process time, inoculum size and initial pH gave a process model with a coefficient of determination R 2 of 0.75 and a validated citric acid yield of 88.73 g/l, an improvement of 45.97 fold over the best wild strain. The response surface graphs showed significant interactive effects of input parameters on citric acid formation. This study established the usefulness of UV-mutation and medium optimization in improving the yield of citric acid. This study highlights the practicability of enhancing citric acid yield using mutant strains of A. niger on agro waste such as cassava peels, coupled with a suitable combination of optimal operational parameters. To the best of our knowledge, this work represents the first reference to the utilization of cassava peel-malted sorghum blend in submerged condition for the production of citric acid by A. niger .

Optimization of citric acid production using a mutant strain of Aspergillus niger on cassava peel substrate

Production of starch-gel digesting amyloglucosidase by Aspergillus oryzae HS-3 in solid state fermentation

Optimization of some fermentation conditions for the production of extracellular amylases by using Chryseobacterium and Bacillus isolates from organic kitchen wastes.

Aspergillus flavus andAspergillus niger produce extracellular amylase into the culture medium when grown on basal medium containing 2% (w/v) soluble starch or cassava peel as the sole carbon source. On soluble tarch the highest amylase activities were 1.6 and 5.2 mg of starch hydrolyzed/min per mg protein forA. flavus andA. niger, respectively. When grown on cassava peel, the highest amylase activity in the culture filtrate ofA. flavus was 170-times higher than that on soluble starch, while that ofA. niger was 16-times higher. The mycelial dry weight for both organisms was not significantly affected by the carbon sources. Maximum enzyme activity was obtained at the growth temperature of 29.0±1°C and pH 7 for both organisms. It is concluded that cassava peel might be a better substrate for the production of amylase byA. flavus andA. niger than commercial soluble starch.

Francis A. Awe

Papers

Amylase synthesis in Aspergillus flavus and Aspergillus niger grown on cassava peel