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Bioprocess Platform for the A. sojae PGzyme system

Final Report Summary - PGSYS EXCHANGE (Bioprocess Platform for the A. sojae PGzyme system)

The Pectin-Degrading Enzyme Complex (PEDC) of fungal origin attract attention due to its tremendous industrial potential. Some applications are in retting of flax and vegetable fibers, clarification of fruit juices, extraction of oils from vegetables and citrus peels, manufacturing of paper and pulp, pre-treatment of difficult-to-cook beans and wine manufacturing. It is also observed that applications of pectinases in various fields are increasing, demanding the discovery of new strains producing pectinases with novel properties. Until now, almost all of the commercial preparations containing PEDCs are produced from fungal sources, mainly from Aspergillus niger. PEDCs comprise an number of enzymes, for example endo-polygalacturonase (PGL, EC exo-PGL (EC pectate lyase (EC pectin lyase (EC and pectin methyl esterase (EC This project has searched for PEDC-producing novel strains with industrial potential. Moreover, the project has developed and demonstrated novel bioprocessing routes to alleviate some major drawbacks e.g. a) post-transcriptional and secretion problems associated with cellular regulations, b) process engineering problems attributed to the morphological changes, c) occurrence of catabolic repression, d) high oxygen uptake rates, e) inefficient and costly recovery, f) presence of interfering activities, g) low shelf life or increased dosage needs. Once the manufacturing the enzyme complex becomes feasible at a competitive cost, the production of enzyme concentrates with differential properties, which are suitable to targeted final applications, becomes possible and profitable.

The PGSYS-Exchange Project succeeded in defining and implementing an optimized bioprocessing strategy for the production and downstreaming of pectin-degrading enzymes by utilization of a non-genetically modified strain of Aspergillus sojae. The application of the natural enzyme complex within the food and beverages industry was tailored to specific needs e.g. in juice production, wine manufacturing, and hard-to-cook bean processing.

The microbial production of the PEDC is carried out utilizing the so-called PG-system platform (PGSYS) that includes the utilization of agricultural by-products in solid-state fermentation systems or the utilization of submerged fermentation media –containing suspended substrate particles. The later was designed so as to generate pelleted mycelia that, in turn, provided a low-viscosity system and required a low power input during operation.

The Project has succeeded a) to generate PEDC-producing, non-GMO microbial strains derived from the parental A. sojae, b) to establish solid-state and submerged fermentation routines, c) to provide a general downstream processing route for the recovery of the enzyme complex, and d) to characterize the crude enzyme mixture in relation to the potential final applications.

A. sojae can be considered a novel and safe source of food grade enzymes with unique properties. The utilization of both submerged fermentation (SmF) and solid-substrate fermentation (SSF) approaches has provided a flexible biosynthesis platform that yields concentrates with distinct functional properties. This implied the utilization of novel fungal strains not previously exploited to this end. The work delivered by the PGSYS Consortium has demonstrated high enzyme productivities and the ability to control the culture morphology, which is vitally important for large-scale (submerged) fermentations.

All-in-all PGSYS allowed at debottlenecking of various biology-associated and engineering-related aspects that may hamper an efficient and cost-effective industrial platform for the production of food enzymes.