Saccharification of alkali pre-treated aquatic weeds biomass using partially purified cellulase immobilized on different matrices

Abstract

Enzyme immobilization has gained considerable significance among other techniques for improving the saccharification ability of disparate lignocellulosic biomasses. In this investigation, the partially purified cellulase (approximately 38 kDa) from Glutamicibacter arilaitensis strain ALA4 was immobilized on various matrices (calcium alginate, k-carrageenan, agar-agar, and gelatin) for evaluating saccharification ability of alkali (4% w/v NaOH) pre-treated aquatic weeds (Alternanthera philoxeroides and Brachiaria mutica) biomass. The immobilization of cellulase using various matrices showed improvement in total reducing sugar (TRS) yield and saccharification efficiency of biomasses in the order of calcium alginate > gelatine > k-carrageenan > agar-agar. Calcium alginate immobilized cellulase exhibited maximum TRS and saccharification efficiency of 17.85±0.18 mg/g and 80.32±0.6%, respectively from pre-treated A. philoxeroides biomass. On the other hand, calcium alginate immobilized cellulase exhibited maximum TRS and saccharification efficiency of 19.51±0.2 mg/g and 87.79±0.6%, respectively from pre-treated B. mutica biomass. Further, the thermo-alkali stability, storage stability, and reusability of calcium alginate immobilized cellulase were determined using standard methodologies. The immobilized cellulase showed higher thermo-alkali stability than free cellulase with residual activities of 46.36±3.6 and 40.55±2.6% at 65 °C and pH 10.0, respectively. Likewise, the immobilized cellulase retained its activity for at least 22–24 days of storage at 4 °C. Most importantly, the immobilized enzyme maintained its saccharification ability towards pre-treated A. philoxeroides and B. mutica up to 4th and 5th cycle, respectively. In conclusion, bacterial cellulase can be immobilized on different matrices, particularly calcium alginate for improving the TRS yield and saccharification efficiency of aquatic weeds biomasses.