Recycling of cell culture and efficient release of intracellular fructosyltransferase by ultrasonication for the production of fructooligosaccharides

•Consumption of saccharide revealed lag phase of A. niger 10 h which were smaller extent than A. flavus of 14 h.•Continuous use of pellets by recycling cell culture leads productivity of FOS for avoidance of regular inoculum development.•Release of FTase by ultrasonication increases the harvesting yield of FOS up to 61.43% (w/w) by Aspergillus niger and 70.44% (w/w) by Aspergillus flavus.

Production of fructooligosaccharide (FOS) through efficient cultivation of biotransformation process by fructosyltransferase (FTase) was evaluated by two new isolates, Aspergillus niger and Aspergillus flavus NFCCI 2364. The saccharide consumption revealed lag phase of A. niger in 10 h which were smaller extent than A. flavus of 14 h. For the recycling of cell culture, the pellet cells were continuously reused after 24 h of submerged fermentation by these microorganisms in which FTase activity remains stable in four consecutive cycles in A. niger and six cycles in A. flavus. When freshly prepared pellets were sonicated for efficient release of intracellular FTase, the best transformation reaction was performed at 20 W acoustic power giving conversion yield of FOS 61.43% (w/w) by A. niger and 70.44% (w/w) by A. flavus respectively. This study was shown that the two fungal isolates can serve as veritable source of intracellular FTase for industrial production of FOS.