Highly concentrated populations of Aureobasidium pullulans cells in biocatalytic pullulan production processes

Abstract

Results are presented from studies and a comparative analysis of highly concentrated populations of free and immobilized Aureobasidium pullulans Y-4137 cells in the biocatalytic processes of pullulan production in glucose-containing media. The possibility of effectively using the developed biocatalyst in the form of immobilized cells is demonstrated. The process characteristics are determined for pullulan production from hydrolysates of various sources of renewable feedstocks (Jerusalem artichoke tubers, aspen wood, Chlorella vulgaris microalgal biomass, and potato pulp) under the action of the catalyst. It is established that A. pullulans cells immobilized in a polyvinyl alcohol (PVA) cryogel consume glucose 1.5 times faster and accumulate a 1.7 times higher concentration of the target polysaccharide in the medium than free cells. The immobilized cells can function for at least 15 operating cycles with a slight (no more than 10%) reduction in their metabolic activity. Analysis of the obtained data confirms that cell immobilization in a PVA gel for the production of pullulan allows us to shorten the duration of operating cycles in similar processes by a factor of 1.4 while reaching a comparable yield of the target product.