Strategy to reduce acetic acid in sugarcane bagasse hemicellulose hydrolysate concomitantly with xylitol production by the promising yeast Cyberlindnera xylosilytica in a bioreactor.

The yeast Cyberlindnera xylosilytica UFMG-CM-Y309 has been identified as a promising new xylitol producer from sugarcane bagasse hemicellulosic hydrolysate (SCHH). However, SCHH pretreatment process generates byproducts, which are toxic to cell metabolism, including furans, phenolic compounds, and carboxylic acids, such as acetic acid, typically released at high concentrations. This research aims to reduce acetic acid in sugarcane hemicellulose hydrolysate concomitantly with xylitol production by yeast strain Cy. xylosilytica UFMG-CM-Y309 in a bioreactor by strategically evaluating the influence of volumetric oxygen transfer coefficient (k L a) (21 and 35 h -1 ). Experiments were conducted on a bench bioreactor (2 L volumetric capacity) at different initial k L a values (21 and 35 h -1 ). SCHH medium was supplemented with rice bran extract (10 g L -1 ) and yeast extract (1 g L -1 ). Cy. xylosilytica showed high xylitol production performance (19.56 g L -1 ), xylitol yield (0.56 g g -1 ) and, maximum xylitol-specific production rate (μp máx 0.20 g xylitol ·g -1  h -1 ) at k L a value of 21 h -1 , concomitantly slowing the rate of acetic acid consumption. A faster acetic acid consumption (100%) by Cy. xylosilytica was observed at k L a of 35 h -1 , concomitantly with an increase in maximum cellular growth (14.60 g L -1 ) and reduction in maximum xylitol production (14.56 g L -1 and Y p/s 0.34 g g -1 ). This study contributes to pioneering research regarding this yeast performance in bioreactors, emphasizing culture medium detoxification and xylitol production.