Xylitol Production From Brewer's Spent Grain via Pichia fermentans Fermentation: Optimization, Scaling, and Isolation

Abstract

The primary aim of this study was to investigate the novel application of brewer's spent grain (BSG), a waste byproduct from the brewing industry, as sustainable and cost-effective feedstock for xylitol production using the yeast Pichia fermentans. The process encompassed fermentation optimization, scale-up, and then downstream processing to produce xylitol. Shake flask fermentation was employed to determine optimal conditions, evaluating key parameters including inoculum concentration (12.5%), feedstock (50%), pH (7.0), temperature (30 degrees C), incubation time (96 h), and agitation speed (150 RPM) with a maximum xylitol production of 32.74 g/L. The yield of xylitol increased to 34.57 g/L by scaling up in an 8-L bioreactor within an incubation time of 72 h. Downstream processing, including centrifugation, charcoal treatment, and ethanol purification was performed successfully, recovering xylitol crystals with a purity of 85.90%. Characterization using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and high-performance liquid chromatography (HPLC) confirmed the purity and composition of crystals. This research highlights the economic and environmental advantages of utilizing BSG for xylitol production, offering a sustainable route over conventional substrates.