Synthesis and characterization of microbial fructosyltransferase (FTase) from endophytic Bacillus stercoris S1 for fructooligosaccharide production

Abstract Purpose Presently, there is a rising awareness of the additional health benefits and market potential for functional foods. Among various functional foods short chain Fructooligosaccharides (FOS) have make its prestige in food industry. Therefore, FOS producing enzymes seems very promising as in the future, FOS markets are expected to thriving worldwide. Keeping in view the potential of microbial Fructosyltransferase in FOS production, an attempt has been made to produce FTase of microbial origin followed by its partial purification and characterization. Methods Stevia rebaudiana was exploited to isolate Fructosyltransferase (FTase) enzyme producing endophytic bacteria. Preliminary screening to select FTase producers was done by Triphenyl Tetrazolium Chloride (TTC) plate assay. Fructosyltransferase producer was identified by morphological, biochemical techniques followed by 16S rRNA gene technique. Fructosyltransferase production of B. stercoris S1 was enhanced by optimization of inoculum size, incubation time, temperature, pH of medium, carbon source concentration by following one variable at time method. Partial purification of FTase was achieved by ammonium sulphate precipitation at 30–60%. Partially purified enzyme was characterized for its temperature, pH and shelf stability. Results In total 07 bacterial isolates were isolated. The bacterial isolate S1 was selected as it exhibited maximum zone of hydrolysis (22 mm) in TTC plate assay. Quantitative screening was done in terms of transfructosylating activities. Isolate S1 exhibited 50.06 U/ml. Maximum Fructosyltransferase activity 119.55 U/ml was recorded in nutrient broth supplemented with 60% sucrose at 72 h with an optimized pH of 6.0 at 40 °C. FTase titres after partial purification were 161.25 U/ml with specific activity 497.68 U/mg, purification fold and recovery percent 1.73 and 73.6% respectively. Partially purified FTase were found active in a temperature range 30 0 C to 80 0 C and in pH range of 5.0 to 9.0. FTase was found stable at -20 0 C for 45 days. Conclusion The results obtained showed that the B. stercoris S1 represents a promising source for FTase enzyme that can be efficiently utilized for FOS production.