Among lignocellulolytic enzymes, laccases are the most versatile, broadly specific, and largely studied enzyme with a wide range of biotechnological potential. Putative laccase (CotA) from Bacillus pumilus MK001 was cloned and expressed in E. coli. In addition to soluble bioactive fraction, inactive inclusion body fraction was also harvested and refolded under optimized conditions resulting in 64 % of refolding efficiency. The enzyme was found to be thermostable exhibiting a half-life of 60 min at 80 °C. UV thermal CD spectra also supported the observation as about 9 % increase in β-sheets was recorded after thermal induction. The 3D CotA structure was constructed through homology modeling and the best selected model was verified through PROCHECK, ERRAT, Verify 3D, and PROSA servers. Final 3D model showed potential binding affinities with ferulic acid, caffeic acid, and vanillin. Results of the docking studies were further validated by HPLC analysis which signified the efficient bioconversion ability of CotA.

Thermostable cellulases offer several advantages like higher rates of substrate hydrolysis, lowered risk of contamination, and increased flexibility with respect to process design. In the present study, a thermostable native endoglucanase nEG (EC 3.2.1.4) was purified and characterized from T. aurantiacus RCKK. Further, it was cloned in P. pastoris X-33 and processed for over expression. Expression of recombinant endoglucanase (rEG) of molecular size ~ 33 kDa was confirmed by SDS-PAGE and western blotting followed by in gel activity determination by zymogram analysis. Similar to nEG, the purified rEG was characterized to harbor high thermostability while retaining 50% of its initial activity even after 6- and 10-h incubation at 80 and 70 °C, respectively, and exhibited considerable stability in pH range 3.0-7.0. CD spectroscopy revealed more than 20% β-sheets in protein structure consistently when incubated upto 85 °C as a speculated reason for protein high thermostability. Interestingly, both nEG and rEG were found tolerant up to 10% of the presence of 1-ethyl-3-methylimidazolium acetate [C2mim][OAc]. Values of the catalytic constants K and V for rEG were recorded as 2.5 mg/ml and 303.4 µmol/mg/min, respectively. Thermostability, pH stability, and resistance to the presence of ionic liquid signify the potential applicability of present enzyme in cellulose hydrolysis and enzymatic deinking of recycled paper pulp.

Present article depicts microbiology of starter (Balma) used in traditional solid-state fermentation of alcoholic beverage (Chhang) by Bhotiya tribe of Uttarakhand. It also highlights the importance of herbs in Balma preparation and kinetics of lactic acid and ethanol fermentation under Chhang preparation using Balma. Balma contains 214 9 10 6 cfu/g yeasts, 2.54 9 10 6 cfu/g lactic acid bacteria (LAB) and 1.4 9 10 6 cfu/g other mesophilic bacteria. ITS sequence analysis revealed a rich diversity of yeast comprising of Saccharomyces cerevisiae, Saccharomycopsis fibuligera and Saccharomycopsis malanga in Balma. 16S rDNA sequence analysis revealed Lactobacillus pentosus and Pediococcus pentosaceus among LAB, while amylolytic Bacillus subtilis and B. aerophilus among other bacteria in Balma. Based on the results, it is speculated that herbs such as Inula cuspidata, Micromeria biflora, Origanum vulgare, Rubus sp. and Thymus linearis used earlier by Bhotiya in Balma preparation contribute as a source of yeasts, LAB and amylolytic bacilli. Study also demonstrates that Bhotiya tribe is rational in preparation of starter as they have circumvented the need of plants by using previous year Balma as inoculum and possibility of deficient quality of Balma due to weak colonization of phyllosphere and rhizosphere microbiota. Results suggest that simultaneous saccharification and lactic acid-ethanol fermentation take place in traditional cereal based Chhang fermentation system of Bhotiya.

This study attempted to reduce the enzyme production cost for exploiting lignocellulosic materials by expression of multiple genes in a single host. Genes for bacterial laccase (CotA), pectate lyase (Pel) and endoxylanase (Xyl), which hold significance in lignocellulose degradation, were cloned in pETDuet-1 vector containing two independent cloning sites (MCS). CotA and xyl genes were cloned in MCS1 and MCS 2, respectively. Pel gene was cloned by inserting complete cassette (T7 promoter, ribosome binding site, pel gene, His tag and complete gene ORF) preceded by cotA open reading frame in the MCS1. IPTG induction of CPXpDuet-1 construct in E. coli BL21(DE3) resulted in expression of all three heterologous proteins of ~65 kDa (CotA), ~45 kDa (Pel) and ~25 kDa (Xyl), confirmed by SDS-PAGE and western blotting. Significant portions of the enzymes were also found in culture supernatant (~16, ~720 and ~370 IU/ml activities of CotA, Pel and Xyl, respectively). Culture media optimization resulted in 2, 3 and 7 fold increased secretion of recombinant CotA, Pel and Xyl, respectively. Bioreactor level optimization of the recombinant cocktail expression resulted in production of 19 g/L dry cell biomass at OD600nm 74 from 1 L induced culture after 15 h of cultivation, from which 9, 627 and 1090 IU/ml secretory enzyme activities of CotA, Xyl and Pel were obtained, respectively. The cocktail was also found to increase the saccharification of orange peel in comparison to the xylanase alone. Thus, simultaneous expression as well as extra cellular secretion of these enzymes as cocktail can reduce the enzyme production cost which increases their applicability specially for exploiting lignocellulosic materials for their conversion to value added products like alcohol and animal feed.

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