Process development for efficient xylitol recovery with ultrasound-assisted hybrid crystallization from fermented rice straw hydrolysate.

In line with worldwide initiatives to achieve carbon neutrality and biomass valorization, the present study offers a sustainable bioprocess for xylitol recovery from rice straw hydrolysate (RSH). The process of xylitol recovery and ultrasound-assisted hybrid crystallization from fermented RSH, derived from 14 L fermenter, was optimized. The optimal conditions for crystallization using xylitol rich fermented supernatant of commercial xylose-based media (CFXM) were xylitol supersaturation of 650 ± 13.18 gL-1, crystallization temperature of 0 °C, seed size of 0.8 mm and seed quantity of 0.2 % w/v. A high crystallization yield (Yc) of 74.13% was observed in CFXM, with a crystal weight of 4.81 g in a size ranging from 800-1300 µm. Ultrasound-assisted crystallization, or sonocrystallization (40 °C for 15 min at 50 kHz frequency) of sugar alcohol was used for the first time in xylitol crystallization and its effects were assessed with conventional seeding crystallization. The highest YC of 83.96% was observed in sample sonicated for 15 min along with enhancement of nucleation and crystal growth. Several analytical techniques were used for studying the crystal size, shape, and physicochemical properties of the formed xylitol crystals. Mixture of CFXM and FRSH in the ratio of 30:70 led to an increase in Yc from 33.11% to 49.15% with an average crystal size of 235 µm. Lastly, from 2 kg of RS, 71.28 g xylitol crystals were successfully recovered.