Enhanced Cellulase Production fromBacillus subtilisby Optimizing Physical Parameters for Bioethanol Production

Abstract

Effect of physical parameters such as initial pH, agitation (rpm), and temperature (°C) for cellulase production from Bacillus subtilis AS3 was investigated. Central composite design of experiments followed by multiple desirability function was applied for the optimization of cellulase activity and cell growth. The effect of the temperature and agitation was found to be significant among the three independent variables. The optimum levels of initial pH, temperature, and agitation for alkaline carboxymethylcellulase (CMCase) production predicted by the model were 7.2, 39°C, and 121 rpm, respectively. The CMCase activity with unoptimized physical parameters and previously optimized medium composition was 0.43 U/mL. The maximum activity (0.56 U/mL) and cell growth (2.01 mg/mL) predicted by the model were in consensus with values (0.57 U/mL, 2.1 mg/mL) obtained using optimized medium and optimal values of physical parameters. After optimization, 33% enhancement in CMCase activity (0.57 U/mL) was recorded. On scale-up of cellulase production process in bioreactor with all the optimized conditions, an activity of 0.75 U/mL was achieved. Consequently, the bacterial cellulase employed for bioethanol production expending (5%, w/v) NaOH-pretreated wild grass with Zymomonas mobilis yielded an utmost ethanol titre of 7.56 g/L and 11.65 g/L at shake flask and bioreactor level, respectively.

Enhanced Production of Cellulase from Bacillus licheniformis K‐3 with Potential for Saccharification of Rice Straw

“…Therefore, it is desirable that the cellulases intended for industrial applications must be active and stable under harsh process conditions besides having a long shelf life and high specific activity and broad range temperature and pH stability. However, most of the available microbial cellulases do not meet industrial criteria and are very expensive; therefore, the search for cost‐effective strategies for the production of cellulases with desirable industrial properties is a continuing practice 6–9…”

“…Different genera of bacteria have been reported as endocellulase producers, including Bacillus , Clostridium , Cellulomonas , Ruminococcus , Alteromonas , Acetivibrio , Bacteriodes , and Marinimicrobium sp 5. 9, 13 However, fewer cellulases have been reported particularly from Bacillus spp., which possess industrially desirable characteristics 6 . Bacillus spp.…”

Isolation, Screening and the Influence of Cultivation Factors on Cellulase of Bacteria Isolated From Termites Gut

“…Rice bran was used as agro waste for cellulase production by Bacillus sp. in numerous studies [4,8]. …”

Optimization of Process Conditions for the Production of Holocellulase by a <i>Bacillus</i> Species Isolated from Nahoon Beach Sediments

“…BSS3 with activity 104.68, 91.28 and 68.22 U mL −1 respectively (Abou-Taleb et al, 2009; Sreedevi et al, 2013). Conversely Deka et al (2013) recorded agitation speed of 121 rpm as optimal for CMCase production by B. subtilis. Low agitation speed especially in high viscous CMC broth, may result in low level of Dissolved Oxygen (DO), which may be insufficient for microbial growth and metabolic activity (Sarka and Aikat, 2014).…”