Otimização de meios de cultura para a produção de xilitol com base em hidrolisados hemicelulósicos de bagaço de azeitona extratado

Mestrado em Engenharia Alimentar - Instituto Superior de AgronomiaThe extracted olive pomace (EOP) is the by-product of the olive pomace oil extraction industry, currently used in low value energy applications. In this work, it was studied the valorisation of hemicellulosic fraction of this material to development of the production of pentose-rich hydrolysates for subsequent bioconversion into xylitol. Given the high content of phenolic compounds, some high value-added, it was studied the aqueous pre-extraction (APE). The optimum conditions for APE were found at 100 ºC, 60 min and a liquid to solid ratio (LSR) of 5 g·g-1. To obtain hemicellulosic hydrolysates, it was studied for both APE-treated and untreated EOP using dilute sulphuric acid (3.5%, w/w) at 130ºC for 130 min at different LSR (3, 4 and 5). The hydrolysates obtained were detoxified using different methods which include the adsorption to NaOH and HCl activated charcoal, anionic resins, concentration by evaporation and membranes (nanofiltration). The impact of hydrolysis LSR, detoxification method and supplementation on xylitol production by the yeast D. hansenii, was evaluated. Nanofiltration was the method that enabled the highest removal of inhibitors. The highest xylitol volumetric productivity was 0.30 g·L-1·h-1 (yield 0.42 g·g-1) was obtained for resin-detoxified hydrolysates (pH 5.5). The highest yield, 0.57 g·g-1, was obtained for nanofiltration detoxified hydrolysates supplemented with corn steep liquor, a low-cost supplement with economic advantage