Fecal microbiota of piglets prefer utilizing dl-lactate mixture as compared to d-lactate and l-lactate in vitro

To compare the fermentation characteristics of d-lactate, l-lactate and dl-lactate mixture by fecal microbiota of pigs, in vitro fermentation test was conducted with d-lactate, l-lactate and dl-lactate mixture as substrates, feces of piglets as inocula. The concentrations of lactate and short chain fatty acid (SCFA) were quantified during the fermentation. The composition of bacterial communities in the inocula and 24 h fermentation fluids was analyzed by pyrosequencing. The results showed that, when 5 mmol/l lactate was used, there was no significant difference in utilizing efficiency among d-lactate, l-lactate and dl-lactate mixture, propionate and butyrate were the major end-products converted from lactate. However, when 25 mmol/l lactates were used, a higher utilizing efficiency of dl-lactate mixture and a slower utilizing rate of d-lactate were observed, acetate and propionate became the main end-products. The SCFA proportions were significantly affected by lactate source and its concentration. Pyrosequencing analysis showed that after 24 h fermentation, significant difference in the composition of bacterial communities (genus and OTU levels) was observed among different substrate groups. The results suggest that lactate accumulation in the hindgut is related to the cooperation between microbiota members, and regulating bacterial community may be a possible way to control lactate accumulation.