Bioprodução de xilitol por Kluyveromyces marxianus ATCC 36907 usando hidrolisado hemicelulósico do bagaço de caju: um estudo sobre a influência da temperatura e da agitação

Abstract

Xylitol is a polyol used in food, dental, pharmaceutical and cosmetic industries. Large-scale production of the sugar-alcohol occurs by via chemical, and it is a process that uses high temperatures and pressures, not counting the various purification steps required, making the process of xylitol production very expensive. For this reason, researchers are seeking new processes of production that can be as efficient as traditional modes. The production of xylitol by bioprocesses has several advantages over traditional chemical processes, due to this, many studies on culture media prepared from lignocellulosic hydrolysates have been carried out. Lignocellulosic materials, such as cashew apple bagasse, are low cost sources with potential applications in bioprocesses. In this context, the aim of this study was to evaluate the production of xylitol by biotechnological processes, using the yeast Kluyveromyces marxianus ATCC 36907 and the hemicellulosic hydrolysate from cashew apple bagasse as substrate, as well as to evaluate the optimal conditions of temperature and agitation for this bioproduction. The hemicellulosic hydrolysate was obtained by hydrolysis with dilute sulfuric acid (H2SO4) and applied as culture medium. Initially, the influence of temperature (30 oC, 37 oC, 40 oC e 45 oC) under constant stirring, at 150 rpm, was evaluated. At this stage, the best results were observed at a temperature of 40 oC, using hemicellulose hydrolysate from cashew apple bagasse, obtaining a maximum concentration of xylitol of 5.14 g.L-1, productivity of 0.11 g.L-1.h-1 and xylitol yield (YP/S) of 0.30 g.g-1. For synthetic media, the highest concentrations of xylitol occurred at temperature of 30 oC, for the Dasgupta medium (MD) this concentration was 2.67 g.L-1 and for the Serpa medium (MS) was 2.63 g.L-1. However, when grown in MS, it was observed that the growth in biomass of the microorganism was higher at 37 oC, reaching the concentration of 16.11 g.L-1 of biomass, while the MD showed a growth of 10.47 g.L-1 when at 30 oC. Subsequently, the influence of the agitation (120, 150 e 200 rpm) was evaluated at 40 oC, because it was the temperature that provided the highest yields of xylitol, under these conditions the best results were found in the agitation of 150 rpm, using hemicellulose hydrolysate, whose process values have already been described previously. For synthetic media, the highest concentrations of biomass occurred in the agitation of 200 rpm, for the MD this concentration was 15.71 g.L-1 and for the MS was 16.88 g.L-1. However, MD showed a higher production of xylitol at 150 rpm, reaching the concentration of 0.52 g.L-1, while the MS presented a concentration of 10.47 g.L-1 of xylitol when in the agitation of 200 rpm. With the results presented, it can be considered that the cashew apple bagasse hydrolysate is a potential medium for the biotechnological production of xylitol by the yeast Kluyveromyces marxianus ATCC 36907, being the highest production reached when the process was conducted at 40 oC and 150 rpm.