Enzymic release of cellobiose from sugar beet pulp, and its use to favour vanillin production in Pycnoporus cinnabarinus from vanillic acid

This study was undertaken in order to optimise the release of cellobiose fr om sugar beet pulp by enzymic treatment, and to evaluate the effect of this cellobiose in activating the vanillin production by filamentous fungi. Cel lulose-rich residues were obtained from sugar beet pulp by a pectinase trea tment, and they were then hydrolysed by a commercial cellulase. Various pre treatments (drying, grinding) and storage were applied, in order to modify the physical state of the cellulose-rich residues, such as degree of crysta llinity of cellulose. After cellulase treatment, 51-64% of the initial cell ulose was degraded into cellobiose and glucose, depending on the pretreatme nt. Whatever the pretreatment applied, cellobiose was maximally produced af ter 2-4 h of hydrolysis. Thereafter, cellobiose was degraded by the beta-gl ucosidase present in the commercial cellulase, but this activity could be i nhibited by the addition of D-glucono-delta-lactone. Only in some cases, co uld the extent of degradation of cellulose be related to the physical state of cellulose-rich residues. The best conditions were used to produce large quantities of cellobiose in order to test its influence in the bioconversion of vanillic acid into vani llin by the filamentous fungus, Pycnoporus cinnnbarinus. Addition of cellob iose to a 3-day-old culture yielded a 3.3-fold increase in vanillin product ion when compared to a control culture devoid of cellobiose. (C) 2000 Elsev ier Science Ltd. All rights reserved.