Integrating use of sugarcane bagasse with sugarcane juice for efficient l-lactic acid production through fed-batch simultaneous saccharification and fermentation: Process configurations and kinetic analysis

The present study investigated the utilization of sugarcane juice (SJ) and sugarcane bagasse (SB) for L-lactic acid (L-LA) production by a newly isolated Enterococcus gallinarum TSKKU D-6. SJ was first investigated as a single substrate, yielding 43.9 f 2.9 g-LA/L, with a fermentation efficiency of 72.0 f 0.1 %, based on sucrose content in SJ. On the other hand, simultaneous saccharification and fermentation (SSF) of SB as a single substrate yielded 68.2 f 2.7 g-LA/L, with a fermentation efficiency of 74.1 f 0.0 %, based on cellulose content in SB. SSF of SJ and SB as co-substrates was subsequently carried out to increase the acid production, where SJ was first fermented, followed by the addition of SB to enhance LA titer. Effects of mixing and SB addition strategy on the kinetics and economic feasibility of L-LA production were investigated using a bioreactor equipped with a single and dual impellers, as well as the use of dual impellers under fed-batch SSF. The use of single and dual impellers gave similar L-LA titers of 95.9 f 1.4 and 102.6 f 0.6 g/L, respectively. Nevertheless, the use of dual impellers shortened the processing time, enhancing LA productivity from 0.37 to 1.12 g/(L & sdot;h). As a result, the economic yield and productivity were improved by 7.1 % and 187.5 %, respectively. Better still, performing fed-batch SSF with the use of dual impellers further improved the economic productivity by 8.7 %. This study demonstrated that integrating use of SB as a low-cost substrate considerably enhanced the acid production and lessened the use of SJ. It was also demonstrated that mixing, and process configuration are critical factors determining the process performance.