Enhanced C-5 sugar production from pine needle waste biomass using Bacillus sp. XPB-11 mutant and its biotransformation to bioethanol

Xylan, second most abundant natural polysaccharide after cellulose, has tremendous applications in various industrial processes. There are several xylan degrading catalysts available, but, still, there is continuous quest among the scientific community to search for new hyperactive xylanases. In the present study, the catalytic potential of xylanase from Bacillus sp. XPB-11 was improved using various mutagens. 5-Bromo-Uracil proved to be the best mutagen resulting in stable and hyperactive mutant BU-7 that showed maximum xylanase activity, i.e., 154.16 +/- 2.23 U/mg protein. Further, optimizing the various parameters resulted in 20% enhancement and overall twofold increase in the xylanase activity of mutant, i.e.188.24 +/- 1.80 U/mg protein. This hyperactive mutant released 26.8 +/- 2.17 mg/ml of C-5 sugar from microwave + 0.5 N NaOH pretreated pine needle waste biomass that on fermentation using Kluyveromyces marxianus MTCC 1498 produced 5.34 g/l of bioethanol with 3.89% yield and 93.5% purity. The hyperactive xylanase from Bacillus sp. XPB-11 mutant BU-7, developed in the present study to release C-5 sugar from pine needle waste biomass and its subsequent biotransformation into bioethanol, is of commercial significance to utilize one of the problematic waste biomass from Himalayan Region for its conversion into second-generation biofuel i.e. bioethanol.