%0 Journal Article
%T Enhanced Cellulase Production from Bacillus subtilis by Optimizing Physical Parameters for Bioethanol Production
%A Deepmoni Deka
%A Saprativ P. Das
%A Naresh Sahoo
%A Debasish Das
%A Mohammad Jawed
%A Dinesh Goyal
%A Arun Goyal
%J ISRN Biotechnology
%D 2013
%R 10.5402/2013/965310
%X Effect of physical parameters such as initial pH, agitation (rpm), and temperature (¡ãC) 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¡ãC, 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. 1. Introduction Cellulases have versatile applications in textile, laundry, pulp and paper, fruit juice extraction, and animal feed additives [1]. In addition, they find use in saccharification of lignocellulosic agroresidues to fermentable sugars which can be used for production of bioethanol, lactic acid, and single-cell protein [2]. Bacteria have been widely explored for cellulase production owing to their high growth rate, expression of multienzyme complexes, stability at extreme temperature and pH, lesser feedback inhibition, and ability to withstand variety of environmental stress [1]. Among them, Bacillus sp. continues to be dominant bacterial workhorse due to the capacity to produce and secrete large quantities of extracellular enzymes [3, 4]. However, physical process parameters such as temperature, pH, and agitation speed play a vital role for the cellulase production efficiency of the microorganisms. Agitation speed is an important factor which governs the dissolved oxygen level in the culture broth that affects cell growth of cellulase producing microorganism [5]. However, higher agitation speed has been shown to inhibit cellulase activity [5, 6]. Analogous profile in
%U http://www.hindawi.com/journals/isrn.biotechnology/2013/965310/