INFLUENCE OF AGITATION AND AERATION ON XYLITOL PRODUCTION BY THE YEAST Starmerella meliponinorum

The production of xylitol from pentose-fermenting yeast is closely related to the amount of oxygen present in the culture medium. This study evaluated the effects of agitation and aeration in xylitol production using the yeast Starmerella meliponinorum FRP.09, previously isolated and selected due to its capacity to produce ethanol and xylitol from xylose. Fermentations were conducted in 125 mL flasks with 15 mL of culture medium and shaken at 150 rpm and 200 rpm without forced aeration and compared to fermentation in a static system. To assess the forced aeration, bioreactor was used with an air flow of 0.1 vvm and agitation of 100 rpm, 0.25 vvm / 150 rpm and 0.5 vvm / 200 rpm. Higher agitation and airflow significantly increased the xylose consumption. The yeast S. meliponinorum FRP.09 achieved the best xylitol yield of 0.6 g of xylitol per g of xylose consumed, when the fermentation was conducted with an air flow/rotation speed of 0.5 vvm / 200 rpm in bioreactor and 150 rpm in the fermentation flasks.利用戊糖发酵酵母制备木糖醇的过程，与培养基中的溶氧量紧密相关。本研究以此前经分离筛选获得、可利用木糖合成乙醇与木糖醇的Starmerella meliponinorum FRP.09酵母为实验材料，评估了搅拌与通气条件对木糖醇生产的影响。发酵实验在125 mL三角瓶中开展，装液量为15 mL培养基，分别以150 rpm、200 rpm的转速进行无强制通气的摇床发酵，并以静置发酵体系作为对照；为评估强制通气条件，本研究采用生物反应器开展实验，设置的空气流量与搅拌转速组合依次为0.1 vvm/100 rpm、0.25 vvm/150 rpm及0.5 vvm/200 rpm。实验结果表明，更高的搅拌转速与通气流量可显著加快木糖消耗速率。当发酵分别在生物反应器中以0.5 vvm/200 rpm条件、或在摇瓶体系中以150 rpm条件进行时，S. meliponinorum FRP.09酵母获得了最优木糖醇得率，即每消耗1 g木糖可生成0.6 g木糖醇。