Parametric Study on the Solid Substrate Fermentation of Poly-γ-Glutamic Acid by a Locally Isolated Bacillus subtilis
Author : Tenorio, Aileene Collantes
Major Adviser : Valencia, Jeanne Michelle T.
Major Co-Adviser : Mercado, Margarita A.
Committee Members : Arocena, Rhebner E.; Movillon, Jovita A.
Year : 2016
Month : December
Type : Thesis
This manuscript can be accessed: Only after the consultation with author or adviser
The study was conducted to determine the effects of initial moisture content, initial pH, incubation temperature, and incubation period on the solid substrate fermentation of poly-γ-glutamic acid (γ-PGA) by a locally isolated Bacillus subtilis. In the time profile experiment, soybean curd residue and coconut paring cake were used as substrates for fermentation, and the substrate that produced the highest γ-PGA yield was chosen for the factorial experiment. It was found that soybean curd residue achieved the highest γ-PGA yield (11.70 g/kg). A two-level factorial experiment was done to determine the effects of the initial moisture content (50 and 70%), initial pH (6.0 and 8.0), incubation temperature (30 and 40°C), and incubation period (48 and 60 hours). From the Analysis of Variance, it was found that initial moisture content, initial pH, and incubation temperature significantly increased the γ-PGA yield of the strain using soybean curd residue. The best condition from the factorial experiment, which was at 70% initial moisture content, an initial pH of 8, and an incubation temperature of 40°C, was used for the time profile experiment of the growth and γ-PGA yield of the strain. The results showed that the lag phase of the bacteria using the best condition occurred from 0 to 18 hours, the exponential phase took place from 18 to 36 hours, and the stationary phase was from 36 to 72 hours. At the stationary phase, a maximum γ-PGA yield of 9.65 g/kg was found at 60 hours.
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