Jornal de Microbiologia Alimentar e Industrial

Lactic Acid Production from Almond Hulls

Abstract

Thomas S, Franqui-Villanueva D, Hart-Cooper W, Waggoner M and Glenn G

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.