Screening of Poly-Glutamic Acid (PGA)-Producing Bacillus Species from Indian Fermented Soybean Foods and Characterization of PGA

Abstract

This present work is aimed to screen the PGA-producing Bacillus spp. from naturally fermented soybean foods of Arunachal Pradesh in India and to characterize the poly-glutamic acid (PGA) extracted from Bacillus spp. A total of 50 isolates were screened for high stickiness from 165 bacterial isolates isolated from 34 samples viz., grep chhurpi, peha/paeha, peron namsing, and peruñyaan. Based on 16S rRNA gene sequence analysis, 50 isolates were identified as Bacillus spp. Viscosity of 50 species of Bacillus were measured, out of which 7 species of Bacillus showing ≥0.03 Pa.s (30 cP) of viscosity were selected viz., Bacillus velezensis GC1-42, B. siamensis GC4-36, B. subtilis PH3-21, B. subtilis PN1-14, B. subtilis PH6-29, B. tequilensis PN9-22, and B. safensis subsp. safensis PY1-19 for PGA production. Amino acid analysis of PGA extracted from seven species of Bacillus showed high molecular weight (>600 kDa). B. safensis subsp. safensis PY1-19, isolated from peruñyaan, showed 78.9% of glutamic acid, antagonistic properties against pathogenic bacteria and had the ability to produce phytase with no hemolytic activity. Hence, this strain was selected as a potential starter to prepare peruñyaan at laboratory, and the final product showed high stickiness and viscosity with production of PGA of around 11 g/L.