L-lactic Acid Production Using Cheap Biomass

In this study,cassava bagasse(CB),a by-product contains starch and lignocellulosic fibers,was used to L-lactic acid(L-LA)production based on simultaneous saccharification and co-fermentation.During the process,starch and cellulosic fractions in CB were co-saccharified by cocktail enzymes.Fermentation results indicated that the mixed culture of Lactobacillus rhamnosus and Bacillus coagulans significantly enhanced the L-LA concentration and productivity when compared with the processes based on mono-culturing using the above strains.A highest L-LA concentration and productivity of 112.5 g L-1 and 2.74 g L-1 h-1 were achieved under the optimized conditions.Besides,L-LA yield(based on starch,exclude cellulose and hemicellulose)of 1.19 g/g was also obtained,which means the starch and lignocellulosic sugars were utilized simultaneously without pretreatment.The novel process presented in this work significantly improves the L-LA production from cassava bagasse,which showed promising in economical waste disposal.In order to overcome bottlenecks of the high amount of cellulase consumption and the great number of waste water discharge in lignocellulosic L-lactic acid(L-LA)production,a non-sterilized fed-batch simultaneous saccharification and fermentation(SSF)-membrane separation integration process was established in this study.During the process,the fermentative wastewater,residual nutrients,and residual cellulase that remained in the waste aqueous solution and solid residuals of corn stover were recycled properly.A total of 6 batches operation were carried out by reusing the cellulase and nutrients in the recycled streams.Consequently,a total L-LA yield of 0.389 g g-1(pretreated CS)was achieved,which was 1.20 times higher than that of the conventional process without the waste streams recycling.Correspondingly,wastewater discharge,cellulase and nutrients consumption of this novel process reduced by 73.7%,47.4%,and 86.1%,respectively.To effectively produce second-generation L-lactic acid(L-LA),for the first time,rice straw(RS)was pretreated by dilute ethylenediamine(EDA)and followed by fed-batch simultaneous saccharification and fermentation(SSF)under non-sterilized conditions.Specifically,the impact of pretreatment parameters included EDA concentration and pretreatment temperature on sugars and L-LA productions were evaluated.Results indicated that after pretreatment in 6%(w/v)EDA at 200? for 1 h and following the enzymatic hydrolysis,42.25 g L-1 of total monomer sugars was generated.By batch SSF,the maximized 63.5 ± 3.0 g L-1 and 296.8 g Kg-1 of L-LA can be obtained from the raw RS using Bacillus coagulans LA-15-2.Fed-batch SSF was further conducted and L-LA concentration of 92.5 g L-1 was obtained in the final fermentation broth.Correspondingly,L-LA productivity and yield reached 2.01 g L-1 h-1 and 578.1 g Kg-1 of the pretreated RS,respectively.This study provided a novel environmental-friendly method for L-LA production,which successfully avoided the usage of large amount of inorganic alkali in lignocellulose pretreatment stage.