Process Optimization For Cell Growth And Cellulase Production By Bacillus Sp

Bacillus sp,as well-known aerobic bacteria,are widely used as functional microorganisms.These microorganisms are widespread with efficient cell growth and metabolism,and mostly spore-forming and easy to survive with excellent stress tolerance and environmental suitability.At the same time,complex production of celluase,protease and amylase could be obtained by Bacillus sp,which contribute a lot to agriculture and food industries development.Currently,Cellulase production and optimization by engineered Bacillus sp remain a hot issue and have attached global attentions for years,while seldom study was performed on improved cellulase production by wild type strains.Nevertheless,it was still a long journey for industrial application for engineered Bacillus sp in terms of its unstable property or performance.In this study,Bacillus subtilis LCCC10049,Bacillus licheniformis LCCC10048 and Penicilliums ploymyxa LCCC10023 were selected for cellulase production,fermentation optimization and strains antagonism analysis.By comparing individual fermentation performance of these three strains,culture conditions were optimized during batch or fed-batch fermentation by each single strain and mixed strains,respectively,such as culture temperature,speed,p H,ventilation volume.Detailed conclusions in this study were obtained as follows:（1）The optimized conditions for best cellulase activity of these three strains was was phosphate buffer solution with p H 8.（2）There were no obvious antagonisms or inhibition zones among these three stains at the cell density of 4.4×10⁵cfu/cm²cultured on agar plate.（3）The optimized conditions for cell growth and cellulase production during fed-batch fermentation by B.subtilis LCCC10049 were as follows:glucose controlled at the range of 2-5 g/L,37℃,200 rpm,p H 7 and 1.5 vvm.Compared to batch fermentation performance,the number of effective viable bacteria was increased from 1.1×10¹⁴cfu/m L to 1.3×10¹⁴cfu/m L,cellulase activity remained stable at 0.46-0.47 FPU/m L while cellulase yield was increased by24.8%.（4）The optimized conditions for cell growth and cellulase production during fed-batch fermentation by B.licheniformis LCCC10048 were as follows:glucose controlled at the range of 2-5 g/L,37℃,200 rpm,p H 7 and 2.5 vvm.Compared to batch fermentation performance,the number of effective viable bacteria was increased from 1.0×x10¹⁴cfu/m L to 1.3×10¹⁴cfu/m L,cellulase activity remained stable at 0.46-0.47 FPU/m L while cellulase yield was increased by 31.4%.（5）The optimized conditions for cell growth and cellulase production during fed-batch fermentation by P.ploymyxa LCCC10023 were as follows:glucose controlled at the range of2-5 g/L,30℃,150 rpm,p H 6.5 and 1.5 vvm.Compared to batch fermentation performance,the number of effective viable bacteria was increased from 6×10⁸cfu/m L to 7×10⁸cfu/m L,cellulase activity remained stable at 0.46-0.47 FPU/m L while cellulase yield was increased by19.7%.（6）The optimized conditions for cell growth and cellulase production during fed-batch fermentation by mixed strains of B.subtilis LCCC10049 and B.licheniformis LCCC10048were as follows:glucose controlled at the range of 2-5 g/L,37℃,200 rpm,p H 7 and 1.5 vvm.Compared to batch fermentation performance,the number of effective viable bacteria was further improved to 2.8×10¹⁴cfu/m L with significant increase of 115%,while cellulase activity still remained stable at 0.47 FPU/m L.In this paper,the cellulase production systems of three kinds of Bacillus were constructed,and the feasibility of mixed fermentation of Bacillus subtilis and Bacillus licheniformis was explored.By batch,fed-batch fermentation optimization,the number of effective viable bacteria and cellulase yield were significantly improved,which could provide technical support for industrial application of Bacillus sp.