A two-year project by scientists at Chico State University has examined how to efficiently convert rice and beer waste into biodegradable plastics using fermentation bacteria.

The goal of this research was to produce lactic acid that could be converted into bioplastics using waste products from beer manufacturing and rice processing.

In laboratory experiments, rice bran and rice hulls were first heated and treated with enzymes to accelerate conversion to glucose and subsequently into lactic acid. This pretreatment process converted 40% to 50% of the rice bran and 20% to 30% of the rice hulls to glucose. In the next step of the process, the pretreated rice glucose solution was exposed to Lactobacillus bacteria for five days (with yeast as a nitrogen source). This resulted in a 90% to 100% conversion of glucose to lactic acid from rice bran, and a 40% to 50% conversion rate for rice hulls.

Scientists then molded small amounts of the lactic acid material into flat plastic sheets. A preliminary business case study found that the combined pretreatment and inoculation process could be scaled up to large-scale manufacturing.

This research was presented in Orlando, Florida at the SPE Global Plastics Environmental Conference in March 2009, in Washington, D.C. at a poster session for the Center for Undergraduate Research in May 2009, and in Chicago, Illinois at the Biopolymers Symposium in September 2009.