Arecanut husk: A potential feedstock for enhanced production of endoglucanase by Bacillus subtilis MU S1

Abstract

Abstract The wide range of application of endoglucanase, especially in lignocellulosic bioethanol production has encouraged extensive studies on these enzymes. However, the expensive nature of the enzyme is the prime impediment which limits its widespread use. The use of cheap substrates to replace synthetic ones is one way to reduce the cost. This study examines the prospects of endoglucanase production by Bacillus subtilis MU S1 using five agricultural wastes as carbon source. The agro-wastes namely arecanut husk, banana peduncle, jackfruit outer rind, pepper waste and tamarind husk were screened to check their suitability as carbon source for enzyme production. Among the different agro-wastes, arecanut husk gave the highest endoglucanase activity (328.8 ± 5.2 U/ml). The potential of this medium for the production of various cellulolytic enzymes was investigated. The strain showed simultaneous extracellular secretion of the enzymes tested. To enhance endoglucanase production the arecanut husk medium was optimized via statistical methods. Using Plackett–Burman design three variables namely yeast extract, Na2HPO4 and inoculum size showing positive effect on endoglucanase production were selected. The optimal values of these components were ascertained using central composite design. Endoglucanase activity of 713.62 U/ml was achieved using the optimized medium containing, 1% arecanut husk, 8.38 g/l yeast extract, 0.88 g/l Na2HPO4 and 2.05% inoculum. Optimization of arecanut husk medium led to a 2.2 fold increase in endoglucanase activity. This work reveals the successful exploitation of arecanut husk for cost-effective production of endoglucanase.