Lactic acid bacteria modulate organic acid production during early stages of food waste composting

Lactic acid bacteria are observed during early stages of almost all food waste composting. Among them, 2 types of lactic acid bacteria, Pediococcus (homofermentative lactic acid bacterium) and Weissella (heterofermentative lactic acid bacterium) have been often reported. In this study, the roles of these 2 types of lactic acid bacteria in the composting were tried to elucidate. It has been pointed out that Pediococcus accelerates the composting process by producing lactic acid which prevented acetic acid generation, thus activating indigenous composting microorganisms. On the other hand, this study elucidated that Weissella produced acetic acid of 20 mg g−1 DS, which is harmful to composting microorganisms, resulting in the inhibition of vigorous organic matter degradation. When these 2 coexist in the starting material, whether the composting succceeds or not depends on the ratio of these 2 lactic acid bacteria. If Pediococcus and Weissella ratio was higher than 101.5, acetic acid level was almost 3 times lower than that observed in the composting with their lower ratios of 1 and 10−1, probably because of the interaction of Pediococcus and Weissella resulting in the suppression of Weissella activity, and thus composting was accelerated.