Abstract
The harnessing of biocatalysts from extreme environment hot spring niche for biomass conversion is significant and promising owing to the special characteristics of extremozymes attributed by intriguing biogeochemistry and extreme conditions of these environments. Hence, in the present study 38 bacterial isolates obtained from hot springs of Manikaran (~ 95 °C), Kalath (~ 50 °C) and Vasist (~ 65 °C) of Himachal Pradesh were screened for glycosyl hydrolases by in situ enrichment technique using lignocellulosic biomass (LCB). Based on their hydrolytic potential 5 isolates were selected and they were Bacillus tequilensis (VCB1, VCB2 and VSDB4), and B. licheniformis (KBFB2 and KBFB3). Cellulolytic activity assayed by growth under submerged fermentation showed that B. tequilensis VCB1 had maximum FPA activity (3.38 IU ml−1) in 48 h, while B. licheniformis KBFB3 excelled for endoglucanase (EGA of 4.81 IU ml−1 in 24 h) and cellobiase (0.71 IU ml−1 in 48 h) activities. Among all the thermophilic biocatalysts evaluated, highest exoglucanase (0.06 IU ml−1) activity was observed in B. tequilensis VSDB4 while endoglucanase of B. licheniformis KBFB3 showed optimum specific activity at pH 7 and 70 °C. Further, the presence of celS, celB and xlnB genes in the isolates suggest their possible role in biomass conversion. Protein profiling by SDS-PAGE analysis revealed that cellulase isoforms migrated with molecular masses of 75 kDa. The endoglucanase activity of promising strain B. licheniformis KBFB3 was enhanced in the presence of Ca2+, mercaptoethanol and sodium hypochlorite whereas moderately inhibited by Cu2+, Zn2+, urea, SDS and H2O2. The results of this study indicate scope for the possible development of novel biocatalysts with multifunctional thermostable glycosyl hydrolases from hot springs for efficient hydrolysis of the complex lignocellulosic biomass into simple sugars and other derived bioproducts leading to biomass valorization.
Highlights
Bioprospecting of biomass towards establishment of bio-refineries for augmentation of commodity chemicals and fuel generation warrants mandatory attention
Bio‐trap enrichment for isolating thermophilic GHs producing bacteria Thermophilic glycosyl hydrolases (GHs) producing bacteria were isolated by following bio-trap enrichment technique with various natural substrates rich in cellulose, xylan and lignin at the mouth of hot springs (32°01′60N:77°20′60E) of Himachal Pradesh in India (Manikaran (~ 95 °C), Kalath (~ 50 °C) and Vasist (~ 65 °C)
Isolation and screening of cellulolytic and xylanolytic thermophilic bacteria Screening of bacteria and assay for hydrolytic activity Thermophilic bacteria with cellulolytic and xylanolytic activities were isolated from hot springs (Manikaran (~ 95 °C), Kalath (~ 50 °C) and Vasist (~ 65 °C)) of Himachal Pradesh using from various lignocellulosic substrates viz., pine needles, PABA, vanillin, acid extracted lignin, lignin extracted from black liquor, banana fibre, grapes, paddy straw, crop residue, corncob and sawdust
Summary
Bioprospecting of biomass towards establishment of bio-refineries for augmentation of commodity chemicals and fuel generation warrants mandatory attention. It is recognized that cellulose is the rate-limiting substrate in bioethanol production and more efficient enzymes are required to overcome the cellulose recalcitrance to biodegradation. To overcome this impediment, strategies for novel biomass treatment and conversion are the need of the hour for global utilization of lignocellulosic wastes. Strategies for novel biomass treatment and conversion are the need of the hour for global utilization of lignocellulosic wastes In this context, one of the strategies could be the use of novel biocatalysts with enhanced stability and improved efficiency for biomass valorization. The approach demands a variety of new capabilities which could be only satisfied by microbes from extreme environments
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