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

Area of Science:

• Agricultural Science
• Food Science and Technology
• Biotechnology

Background:

• Rice Bran (RB), Rice Polish (RP), and De-oiled Rice Bran (DORB) are underutilized by-products of rice milling.
• These materials contain anti-nutritional factors (ANFs) and have limited nutrient bioavailability, hindering their wider application.
• Yeast fermentation offers a potential strategy to improve the nutritional quality and utilization of these agro-industrial by-products.

Purpose of the Study:

• To investigate the efficacy of yeast fermentation using *Saccharomyces cerevisiae* in enhancing the nutritional profile of RB, RP, and DORB.
• To optimize fermentation parameters including yeast concentration, moisture level, and incubation time for maximum nutritional improvement.
• To evaluate the impact of fermentation on proximate composition, metabolizable energy, and phosphorus availability.

Main Methods:

• A 2x3x9 factorial experiment was conducted using RB, RP, and DORB.
• Fermentation was performed with Baker's yeast (*Saccharomyces cerevisiae*) at 1.0% and 2.0% levels, with moisture content at 40%, 50%, and 60%.
• Incubation was carried out at 39°C for up to 48 hours, with measurements of gas production, ethanol yield, proximate composition, and available phosphorus (AvP).

Main Results:

• Rice Bran (RB) showed the highest fermentation efficiency, with significant increases in crude protein (23.1%), ether extract (nearly doubled), metabolizable energy (27.0%), and AvP (0.27-0.42).
• Rice Polish (RP) fermentation led to a 18.2% reduction in crude fiber, a 66% increase in ether extract, a 9.5% increase in metabolizable energy, and improved AvP (0.95-1.26).
• De-oiled Rice Bran (DORB), despite lower fermentability, exhibited notable nutritional gains: 15.6% increase in crude protein, 18.9% reduction in crude fiber, 294% increase in ether extract, 22% increase in metabolizable energy, and improved AvP (0.82%-1.02%).

Conclusions:

• Yeast fermentation significantly improves the nutritional potential of RB, RP, and DORB, making them more valuable feed ingredients or food components.
• RB demonstrated the highest potential for nutritional enhancement through fermentation, particularly in protein, energy, and phosphorus content.
• Even with lower fermentability, DORB benefits substantially from this process, showing improvements in protein, fiber reduction, and phosphorus availability.