The optimization of fermentation conditions for producing cellulase of Bacillus amyloliquefaciens and its application to goose feed

Abstract

The proper culture conditions for producing cellulase of Bacillus amyloliquefaciens S1, isolated from the cecum of goose was optimized by single-factor experiment combined with orthogonal test. The properties of the cellulase were investigated by DNS method. The appropriate doses of B. amyloliquefaciens S1 were obtained by adding them to goose feed. It indicated that the suitable culture conditions of producing cellulase were the culture temperature of 37°C, the initial pH of 7.0, the incubation time of 72 h and the loaded liquid volume of 75 ml per 250 ml. The effects of each factor on producing cellulase by B. amyloliquefaciens S1 were as follows: initial pH > incubation time = culture temperature > loaded liquid volume. The optimum reaction temperature and pH were 50°C and 7.0, respectively. This enzyme is a kind of neutral cellulase that possesses resistance to heat and acidity. It showed high activity to absorbent cotton, soya bean meal and filter paper. By adding different doses of B. amyloliquefaciens S1 to the goose feed, it was found that the egg production, average egg weight, fertilization rate and the hatching rate were promoted both in experiment 1 (1.5 g kg^-1) and experiment 2 (3 g kg^-1). Also the difference of egg production, fertilization rate and hatching rate between experiment 1 and control group was obvious (p < 0.05), and the average egg weight was significantly increased in experiment 2 (p < 0.05).

Keywords: Bacillus amyloliquefaciens S1; cecum of goose; cellulase; culture conditions; enzyme properties; goose feed.

Figure 1.

Optimization of fermentation conditions of cellulase secreted by B. amyloliquefaciens S1. (a) Effect of fermentation temperature on enzyme production; (b) effect of fermentation time on enzyme production; (c) effect of initial pH of medium on enzyme production; (d) effect of carbon and nitrogen ratio of medium on enzyme production and (e) effect of medium volume aeration on enzyme production.

Figure 2.

Properties of cellulase secreted by B. amyloliquefaciens S1. (a) Effect of temperature on cellulase activity; (b) effect of pH on cellulase activity; (c) thermal stability; (d) pH stability; (e) effect of metal ions on cellulase activity and (f) selectivity of cellulase to substrates. 1: CMC-Na; 2: cassava dregs; 3: absorbent cotton; 4: soya bean meal; 5: filter paper; 6: microcrystalline cellulose.