Production, characterization and application in the saccharification of agro-industrial wastes of a thermostable and halotolerant endoglucanase

Abstract

This study describes the production, characterization, and application of an endoglucanase from Penicillium roqueforti ATCC 10110 using lignocellulosic agro-industrial wastes as the substrate during solid-state fermentation. The endoglucanase was generated after culturing with different agro-industrial wastes for 96 h without any pretreatment. The enzyme was characterized by evaluating the effects of temperature and pH. The highest activity was obtained at 50 °C and pH 4.0. Additionally, the enzyme showed stability in the temperature and pH ranges of 40 °C to 80 °C and 4.0 to 5.0, respectively. The addition of metal ions Ca2+, Zn2+, Mg2+, and Cu2+ increased enzymatic activity, whereas on addition of organic solvents, the activity remained above 91%. Halotolerance as a characteristic of the enzyme was confirmed when its activity increased by 35% on addition of 2M NaCl. The endoglucanase saccharified sugarcane bagasse, coconut husk, wheat bran, cocoa pod husk, and cocoa seed husk. Scanning electron microscopy (SEM) confirmed the enzyme’s action in deconstructing all lignocellulosic materials. The Box–Behnken design was employed to optimize fermentable sugar production by evaluating the following parameters: time, substrate, and enzyme concentration. Under ideal conditions, 253.19 mg/g of fermentable sugars were obtained following the saccharification of wheat bran without any pretreatment, which is 41.5 times higher than that obtained without optimizing the three parameters. This study presents a thermostable, halotolerant endoglucanase that is resistant to metal ions and organic solvents with the potential to be applied in producing fermentable sugars for manufacturing biofuels from agro-industrial wastes.