Simplex centroid mixture design to improve l-asparaginase production in solid-state fermentation using agroindustrial wastes

Agroindustrial wastes, such as wheat bran, soybean meal, cottonseed meal and orange peel, were used individually or in mixtures as fermentation feedstock for l-asparaginase production from Aspergillus niger LBA 02 under solid-state fermentation using a simplex centroid mixture design. At 24 h of fermentation, most of the interaction effects observed were antagonistic and the highest l-asparaginase activity was obtained with cottonseed meal as the feedstock. At 48 h of fermentation, synergistic effects were found for two binary formulations and one quaternary formulation and increase in the l-asparaginase activity ranged from 0.69 to 73.44 fold. At 72 h of fermentation, synergistic effects were also found for two binary and one quaternary formulation and increase ranged from 0.47 to 4.26 fold. At 96 h of fermentation, synergistic effects were found for four binary and one quaternary formulation and increase ranged from 0.44 to 17.84 fold. The enzyme production reached the highest value after 96 h of fermentation, and the optimum conditions predicted for l-asparaginase production were found to be a ternary mixture of wheat bran (1/3), soybean meal (1/3) and cottonseed meal (1/3) with increases of 71.53, 13.53 and 13.53 fold in l-asparaginase production as compared to the individual feedstocks, respectively. The predicted activity was 94.21 U g−1, which showed no significant difference (p<0.05) from the experimental l-asparaginase activity of 89.22 U g−1. Therefore, mixtures contained wheat bran (1/3), soybean meal (1/3) and cottonseed meal (1/3) may be added to improve the l-asparaginase production with low cost.