Genetic control of protein and glucose-anabolic-enzyme syntheses by Saccharomyces cerevisiae in the fermentation of a Nigerian rice, Oryza sativa variety “Igbimo”

This work aimed at the control of the production of protein and glucose-anabolic-enzyme (GAE) by Saccharomyces cerevisiae during the fermentation of a Nigerian rice, Oryza sativa variety “Igbimo”. The yeast was mutated with ethylmethyl sulphonate. The variants and the parental yeast were separately inoculated into cooked rice and allowed to ferment at 27℃ for 7 days after which protein content and glucose-anabolic-enzyme synthesis were determined using Dinitrosalicylic acid and Biuret reagents techniques. Mutants with varying capacities to form protein and GAE were obtained. Glucose-Anabolic-Enzyme (GAE) activity ranged from 0.25 to 12.06 Units forming five groups (classes 1, 2, 3, 4 and 5) with the average activity of 0.52, 1.52, 2.28, 4.04 and 10.63 Units respectively compared with that (0.38 Unit) of the parent strain. All the mutants synthesized protein although many of them produced it at lower level while others at higher level than the wild-type. The highest (5.92 mg/mL) and lowest (0.10 mg/mL) levels protein producers are mutants 44 and 14 respectively. Mutants No. 4, 7, 22 and 78 formed total protein similar in concentrations (1.46, 1.46, 1.45 and 1.45 mg/mL) to that of the wild yeast (1.46 mg/mL). These three sets of protein concentration have ratios 4.1 (highest), 0.07 (lowest) and 1.0 (normal) to that of the parental yeast.