STATISTICAL OPTIMIZATION OF A NOVEL LOW-COST MEDIUM BASED ON REGIONAL AGRO-INDUSTRIAL BY-PRODUCTS FOR THE PRODUCTION OF PROTEOLYTIC ENZYMES BY Bacillus cereus

Abstract

Bacillus sp. are specific producers of peptidase amongst bacteria and peptidase enzymes and are of significant ones due to their multifarious applications. Advances in industrial biotechnology offer potential opportunities for economic utilization of agro-industrial by-products for many biochemical reactions. Due to their rich organic nature, they can serve as an ideal substrate for the production of different value added products like peptidases. In the present work, an attempt was made to optimize different variables by Taguchi methodology for the production of peptidase using agro-industrial by-products hydrolyzed by a Bacillus cereus strain, resulting in brewer's spent grain (BSG) being the optimal organic substrate. Subsequently, operative variables for the BSG were investigated using Taguchi methodology in order to maximize the enzyme production. Additionally, the main medium components were optimized using a mixture design. Finally, the production of peptidase by B. cereus was investigated; also the possible interaction with other proteolytic microbial strains was evaluated. A notorious synergistic effect was observed when B. cereus was inoculated with Pseudomonas sp. These brought a triple benefit, first, opening the possibility to produce technical enzymes at low cost, second, giving greater value to a food industry by-product, and third, reducing the environmental impact caused by the product removal directly into the environment.

Keywords:

• medium optimization
• mixture design
• peptidase
• statistical designs
• taguchi design

Notes

Note. Each result is the mean of three determinations; standard errors were less than 10% of the means.

Note. Each result is the mean of three determinations; standard errors were less than 10% of the means.

Note. NA: not analyzed.

Note. R-squared: 0.878; coefficient of variation: 79.039; root MSE: 0.052; mean: 0.066. A: Organic substrate; C: metal ions; E: initial pH; asterisk indicates significant terms.

Note. R-squared: 0.988; coefficient of variation: 41.627; root MSE: 0.046; mean: 0.110. A: Organic substrate; C: metal ions; asterisk indicates significant terms.

Note. Each experimental result is the mean of three determinations; standard errors were less than 10% of the means.

Note. Asterisk indicates significant.