Thermophilic microbes producing industrially important enzymes from the Manikaran geothermal springs of Himachal Pradesh (India) and their application in biomass saccharification

Thermophilic enzymes are valuable in industries because they can function under harsh conditions like elevated temperatures, pH extremes, salinity, high substrate loading, and stringent processes. Geothermal springs offer the best source for identifying and isolating thermophiles for obtaining thermozymes. The present study isolated thermophilic microbes from the Manikaran hot springs of Himachal Pradesh, India by selective enrichment on solid substrates. The thermophilic bacteria were screened for industrially relevant enzymes. Among the 40 thermophilic isolates, 12 morphologically distinct isolates showed enzymatic activities of one or more enzymes like cellulase, amylase, protease, lipase, and ligninase. Potential thermophilic bacteria were identified based on 16S rRNA gene sequencing and phylogenetic profiling. Nine isolates belonged to Brevibacillus borstelensis, two belonged to Bacillus subtilis, and one was identified as Ba. licheniformis. These isolates thrived in a wide pH range (from 4.00 to 12.00) and tolerated temperatures of up to 80 °C. Isolates MC4 and MX18 were the best cellulase producers, with pH optima of 7.00 and 6.00 and temperature optima of 60 °C and 50 °C, respectively. The CMCase (carboxymethyl cellulase), FPase (filter-paper cellulase), and Avicelase (avicel hydrolase) activities were 10.37 U/mL, 3.78 U/mL, 0.17 U/mL and 9.69 U/mL, 3.0 U/mL, 0.14 U/mL from isolates MC4 and MX18, respectively. The cellulases produced by isolates MC4 and MX18 yielded 52% and 65% saccharification efficiency with corncob as the substrate. Thus, the study identified potential thermophilic bacteria producing industrially essential enzymes for biomass hydrolysis at high titer.