The isolation of useful bioproducts remaining from the large-scale fermentation of penicillium chrysogenum

Abstract

Chitin, a homopolymer of ß-(1-4) linked N-acetyl D-glucosamine units, and its deacetylated derivative chitosan have unique properties that may allow their utilisation in a diverse array of high-value applications. Currently chitinous materials are commercially produced from the waste products of the seafood processing industry, this supply is seasonal and the extraction procedures required harsh, resulting in products with heterogeneous characteristics. In this work novel methods of extraction of chitinous material from the dry fungal biomass remaining from the large-scale fermentation of Penicillium chrysogenum in the penicillin manufacturing industry were investigated, with the aim of avoiding or minimising the harsh chemical treatments. This work was carried out in partnership with Angel Biotechnology, who produce penicillin commercially and provided the waste biomass. It was determined that the chitinous material present in this biomass was too intractable for this to be a suitable commercial source of chitin, as large quantities of non-chitinous polysaccharide impurities remained in the product. Attempted enzymatic degradations of the fungal cell wall did not increase the level of purity of the extract. Comparison to other fungal sources of chitinous material indicated that P. chrysogenum does not provide the most efficient source of chitinous material. During the course of these studies it became apparent that there is no agreed literature procedure for the determination of the degree of deacetylation (DDA) of chitinous material, this characteristic is essential in determining the physiochemical properties of the polymer. In reviewing the procedures available we concluded that (^15)N solid-state NMR offered the most reliable method, however, its use was limited by the low natural abundance of (^15)N. We therefore developed a novel, efficient and directed strategy for the (^15)N labelling of chitinous material in fungal cells walls. This allows the direct determination of the DDA of chitinous material in whole fungal cells without the need for lengthy extraction procedures. The whole cell CPMAS ssNMR techniques developed may find many applications, such as monitoring cell wall biogenesis in response to varying nutrient conditions. Additionally, this may allow the rapid screening of fungal species to determine the concentration and DDA of chitinous material.