P79: Biotechnological production of xylitol from cashew apple bagasse hydrolyzate

Xylitol, a polyol obtained from D-xylose with wide application in food and pharmaceutical industries, is currently produced large-scale by chemical processes, but due to the high operating costs inherent of this operation, unconventional routes, such as the ones involving biotechnological paths, have been investigated. Cashew apple bagasse (CAB), which is an agroindustrial by-product obtained from a typical fruit found in Brazilian Northeast, is able to undergo hydrolysis and provide D-xylose, which can be metabolized by microorganisms and produce xylitol. This study initially evaluated the capability of three yeast strains to produce xylitol from synthetic medium containing D-xylose (MX) as main carbon source. After previous experiments, the two microorganisms which best performed in MX were selected for evaluation in the medium obtained from acid hydrolysis of cashew apple bagasse (HCAB). These microorganisms were able to metabolize the glucose and xylose present in HCAB and were observed to produce ethanol and xylitol. Important factors to be highlighted in process optimization are amendments in the hydrolyzate formulation, such as the performing of a detoxification to remove interfering substances, the adding of supplementary nitrogen sources, temperature and aeration control. Experiments carried out in HCAB concentrate with higher concentrations of sugars and, consequently, acetic acid, showed the need for a detoxification treatment to reduce the levels of this potential interferer, so as to make it possible to increase the polyol production. Therefore, the hemicellulosic cashew bagasse hydrolyzate is a low-cost renewable alternative source which has proved to be effective in xylitol microbial production.