Abstract
Bacteria isolated from thermophilic environment that can produce cellulase as well as utilise agro-waste biomass have a high potential for developing thermostable cellulase required in the biofuel industry. The cost for cellulase represents a significant challenge in converting lignocellulose to fermentable sugars for biofuel production. Among three potential bacteria examined, Bacillus licheniformis 2D55 (accession no. KT799651) was found to produce the highest cellulolytic activity (CMCase 0.33 U/mL and FPase 0.09 U/mL) at 18–24 h fermentation when grown on microcrystalline cellulose (MCC) as a carbon source in shake flask at 50 °C. Cellulase production process was further conducted on the untreated and NaOH pretreated rice straw (RS), rice husk (RH), sugarcane bagasse (BAG) and empty fruit bunch (EFB). Untreated BAG produced the highest FPase (0.160 U/mL), while the highest CMCase (0.150 U/mL) was supported on the pretreated RH. The mixture of untreated BAG and pretreated RH as agro-waste cocktail has remarkably improved CMCase (3.7- and 1.4-fold) and FPase (2.5- and 11.5-fold) compared to the untreated BAG and pretreated RH, respectively. The mechanism of cellulase production explored through SEM analysis and the location of cellulase enzymes of the isolate was also presented. Agro-waste cocktail supplementation provides an alternative method for an efficient production of cellulase.
Highlights
Each year, there are millions of tonnes of lignocellulosic wastes being generated from the agricultural, agro-industrial and forestry industries, which pose a major disposal problem
Findings on this study have presented that temperature has drastically rose at day 2 with its peak at 68 °C on day 4, which was slowly declined until the end of composting process (Fig. 1)
Moisture content during the composting period was found within 58 to 70%, which is in agreement with that conducted by Yahya et al [1]
Summary
There are millions of tonnes of lignocellulosic wastes being generated from the agricultural, agro-industrial and forestry industries, which pose a major disposal problem. Cellulase hydrolyses the β-1,4-D-glucan linkages of cellulose to liberate cello-oligosaccharide, cellobiose and glucose as its major end products. The major concern in utilising lignocellulose for bioethanol production is the cost of cellulase, which is usually produced from expensive substrates [3, 4]. It is still expensive despite the huge efforts given to improve its activity and productivity [5]. The utilisation of cheap and readily available agro-waste material in producing cellulase could possibly reduce its production cost and price. The cost of cellulase could be reduced by four to five times through screening, strain reconstruction and innovation in the production process [6]
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