RESUMO
A total of 41 isolates were obtained from various samples (soil, mud, and water) of Surajkund hot spring, Jharkhand, atthree different isolation temperatures of 50C, 60C, and 70C. However, our interest was in the thermophilic strains thatwere isolated at 60C and 70C. Four isolates at 70C (BITSNS038, BITSNS039, BITSNS040, BITSNS041) are theproducers of thermozymes, namely amylase, xylanase, and cellulase, respectively. The highlights of the present study alsoshowed that three out of four isolates demonstrated all three enzymatic activities, i.e. amylolytic, xylanolytic and cellulolytic on agar plate assay conditions at 70C. One of the isolates, BITSNS038, was further chosen for phenotypiccharacterization as well as 16S rRNA gene sequencing and was affiliated to Geobacillus icigianus. The presence ofGeobacillus icigianus was reported first time from hot spring, Surajkund, which showed amylolytic index of 1.58,xylanolytic index of 1.5 and cellulolytic index of 2.3 based on plate assay, and amylase activity of 0.81 U/mL, xylanaseactivity of 0.72 U/mL and very less cellulase activity of 0.15 U/mL after 24 h of growth in submerged conditions. Oneisolate at 60C BITSNS024 was found to exhibit maximum amylase activity with an enzymatic index value of 3.5 and wasidentified as Anoxybacillus gonensis.
RESUMO
The combined effects of significant physical and chemical factors affect hyperthermostable ß amylase production under submerged fermentation by Bacillus subtilis DJ5. The above was studied using the experimental design and response surface methodology. A 23 full-factorial central composite design was chosen to analyze interactions among three factors i.e. substrate concentration, medium pH and incubation temperature. The experimental data were fitted into a polynomial model for the yield of enzyme and an optimum level was arrived at with optimized conditions. Solving the coded values using Excel equation function indicated that maximum enzyme production is possible at a substrate concentration of 7.07 mg mL-1, pH 6.622 and temperature of 35.435°C. Such prediction was validated with practical experiments in which, at the prescribed condition maximum yield of 15.62 U mg-1, nearly 1.5 fold higher than non-optimized condition was observed.
Os efeitos combinados de fatores físicos e químicos significativos influenciam a produção hipertermoestável de amilase ß sob fermentação submersa por Bacillus subtilis DJ5. O esquema experimental e metodologia de superfície de resposta foram usados, com 23 planejamento fatorial composto, para analisar as interações entre os três fatores, ou seja, concentração de substrato, pH médio e temperatura de incubação. Os dados experimentais foram ajustados a um modelo polinomial para a produção de enzima e chegou-se a um nível ótimo através de condições otimizadas. A solução dos valores codificados por equação de Excel indicou que a produção máxima da enzima é possível a uma concentração de substrato de 7,07 mg mL-1, pH 6,622 e temperatura de 35,435°C. Tal previsão foi validada com experimentos práticos, onde na condição prescrita de rendimento máximo de 15,62 U mg-1, foram observados cerca de 1,5 vezes maior do que o estado não otimizado.