Lactic acid production from almond hulls

Authors: Thomas, Steven; Franquivillanueva, Diana; Hart-Cooper, William; WAGGONER, MIKE - Grow Plastics; Glenn, Gregory - Greg

Submitted to: Journal of Food & Industrial Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2019
Publication Date: 1/18/2019
Citation: Thomas, S.M., Franquivillanueva, D.M., Hart-Cooper, W.M., Waggoner, M., Glenn, G.M. 2019. Lactic acid production from almond hulls. Journal of Food & Industrial Microbiology. 5(1):128.

Interpretive Summary: Lactic acid used in making the corn plastic, poly (lactic acid), is typically made from the fermentation of corn starch. As global food reserves become more limited, it is important to find more sustainable feedstocks for making non-food products. Scientists from ARS scientists in Albany, Ca found that almond hulls contain enough fermentable sugars to make high quality lactic acid. This research could help develop new uses for agricultural wastes such as almond hulls and help minimize the use of food reserves for making non-food products.

Technical Abstract: Lactic acid (LA) is a commodity chemical used in pharmaceuticals, bio plastics, and food, home and personal care products. It is commercially produced by fermentation of corn starch, which requires large amounts of land and water. Almond hulls are a cheap agricultural byproduct that have high sugar content and could be used as a carbon source in the fermentation of lactic acid. In this study, we fermented almond hulls using a mixed culture from primary sludge and a mono-culture from Lactobacillus rhamnosus and compared the production of lactic acid from almond hulls against that of other alternative feedstocks. Other feedstocks tested included corn stover and pine wood as lignocellulosic feedstocks, food waste, glucose, glycerol as a cheap chemical byproduct and sorbitol as a negative control. In both mixed culture and pure culture, almond hulls (maximum values for yield 0.55 g/g biomass, productivity 2.8 g/L/h, >99% L-LA) gave higher yields than food waste (maximum values for yield=0.44 g/g biomass, productivity=1.2 g/L/h, 84-95% L-LA), but lower yields than glucose (maximum values for yield 0.95 g/g biomass productivity 4.2 g/L/h, = 96% L-LA). Pine wood and corn stover did not produce lactic acid efficiently under the mixed culture conditions tested. The results of this study lend support for the use of almond hulls as an affordable feedstock for the production of lactic acid.