A. P. Gandhi

Citric acid production from Okara (soy-residue) by solid-state fermentation

Abstract Okara (soy-residue), a cellulosic byproduct of the soymilk and tofu (soypaneer) industry, was used for the production of citric acid by solid-state fermentation using a cellulolytic Aspergillus terreus and citric-acid-producing Aspergillus niger . Okara supplemented with ammonium sulphate (0·10% N) when fermented by A. niger with simultaneous saccharification using A. terreus at pH 8·3 and incubation temperature of 30°C resulted in production of 5·10 g citric acid/100 grams dry solids (gds) by the eleventh day.

Use of agarose-entrapped Aspergillus niger cells for the production of citric acid from soy whey

Aspergillus niger cells immobilized in agarose beads were utilized for the productin of citric acid from soy whey, a by-product generated during the tofu-making process. Soy when samples supplemented with 10% sucrose were inoculated with 10% (w/v) free and immobilized cells and incubated at 30°C in a shaker water bath at a speed of 200–220 rpm. Maximal citric acid yields of 21 g/l and 27 g/l with free and immobilized cells, respectively, were recorded on the 10th day under repeated batch conditions.

Solid-state fermentation of soyhull for the production of cellulase

Soyhull, a lignocellulosic material produced in large amounts during soybean processing, was utilized for cellulase production through solid-state fermentation. Of five known fungi, Phanerochaete chrysosporium gave maximum yields of the enzyme. Optimum pH of the substrate and temperature of incubation were 4·0 and 25°C. Under optimized conditions, the addition of urea at 2% (w/w) could enhance the enzyme yields to 74·8 IU/gram dry solids (CMCase) and 29·1 IU/gds (FPase) from the initial values of 27·5 IU/gds (CMCase) and 12·2 IU/gds (FPase). The optimum size of the inoculum was 1·0 × 104 viable spores/gds.

Hydrolysis of flatulence-causing galacto-oligosaccharides by agarose-entrapped Aspergillus oryzae cells

Abstract Aspergillus oryzae cells were entrapped within agarose beads. These entrapped cells, having α-galactosidase activity of 0.72 IU/ml, were used for hydrolyzing flatulence-causing galacto-oligosaccharides present in soymilk. The total of 52% raffinose, 70% stachyose, and 66.3% total oligosaccharides of soymilk was observed to be hydrolyzed in 8 h at 50°C by these immobilized cells.

Preparation of soya bean meal protein hydrolysate by agarose-entrapped Bacillus subtilis cells

Abstract Bacillus subtilis cells entrapped in an agarose gel matrix were used for the hydrolysis of soya meal protein. A maximum hydrolysis in terms of tyrosine content 31·8 mg tyrosine) was observed at pH 7·0–7·5 and temperature 55°C in 4 h with a cell concentration of 25% (w/v). The hydrolysate consisted of 3·8% (w/v) solid content.