Fermentation Efficiency of Rice Bran, Rice Polish, and De-Oiled Rice Bran for Nutritional Upgrading and Bioethanol Production.

Rice Bran (RB) and Rice Polish (RP) are by-products of the rice milling industry where further oil extraction from RB produces De-oiled Rice Bran (DORB). These by-products are often underused because they contain anti-nutritional factors (ANFs), have a high fiber content, and limited nutrient availability. This study aimed to improve the nutritional potentiality through yeast fermentation. RB, RP and DORB were employed in a 2 × 3 × 9 factorial experiment with Baker's yeast (Saccharomyces cerevisiae) at 1.0% and 2.0% level, with three moisture levels (40%, 50%, 60%) and 9 times (0, 6, 12, 18, 24, 30, 36, 42, 48 h), incubated at 39°C in 100 mL glass syringe. The fermentation efficiency was measured by cumulative gas production, ethanol yield, change in proximate composition, and availability of phosphorus (AvP). Fermentation of RB was maximum, with 2932 mL/100 g DM gas at 6 h and 3.49 g/100 mL ethanol at 48 h at 60% moisture level and 2.0% yeast. Its crude protein (CP) was raised by 23.1%, crude fiber (CF) was lowered by 20.1%, ether extract (EE) doubled nearly, metabolizable energy (ME) by 27.0%, and AvP. 0.27-0.42. RP was found as moderately fermentable by 713 mL/100 g DM gas and 1.45 g/100 mL ethanol, whereas nutritional improvement was noticed with an 18.2% reduction of CF, a 66% increase in EE, a 9.5% increase in ME, and AvP from 0.95 to 1.26. DORB was least fermentable but showed considerable nutritional improvements, including a 15.6% improvement in CP, an 18.9% reduction in CF, a 294% increase in EE, a 22% increase in ME, and a change in AvP from 0.82% to 1.02%. Fermentation significantly improved the nutritional potential of RB, RP, and DORB, with RB having the highest protein, ME, and AvP. Though RB was most fermentable, RP was partially improved, whereas DORB, despite low fermentability, had high protein, fiber removal, and AvP.