Efficient production of polymer-grade l-lactate by an alkaliphilic Exiguobacterium sp. strain under nonsterile open fermentation conditions

In this study, a newly isolated alkaliphile Exiguobacterium sp. strain 8-11-1 was used to produce optically pure l-lactate. With an initial glucose concentration of 80 g/L, a high overall l-lactic acid productivity of 8.15 g/L/h was achieved using NaOH as a neutralizing agent. The fed-batch fermentations were carried out under both sterile and nonsterile conditions. Under the nonsterile condition, 125 g/L l-lactic acid was obtained with a high percent yield and average productivity of 98.33% and 3.79 g/L/h, respectively. These values were consistent with the results from sterile condition. No d-isomers of lactic acid were detected, resulting in an optical purity of 100% in both conditions. The high levels of optically pure l-lactic acid produced by Exiguobacterium sp. 8-11-1, combined with the ease of handling and low costs associated with the open fermentation strategy, provide a novel and potentially important approach for l-lactic acid production in the future.