Ionic liquid and diluted sulfuric acid combinatorial pretreatment for efficient sugarcane bagasse conversion to L-lactic acid

An economical pretreatment method is needed to produce the L -lactic acid from renewable biomass. Six different combinatorial experiments including choline chloride [Ch][Cl], 1-ethyl-3-methylimidazolium chloride [Emim] [Cl], and 1-butyl-3-methylimidazolium chloride [Bmim][Cl], diluted acid sulfuric acid (DSA), and two ionic liquids (ILs) were tested. Ionic liquid (ILs) step performed at 90, 110, and 130 degrees C. The cellulose content of sugarcane bagasse (SCB) increased from 42.1 % (raw material) to 74.6 % (combinatorial pretreatment with DSA and [Emim][Cl]) to 79.9 % (after water washing). Pretreated SCB was employed in enzymatic saccharification and L -lactic acid fermentation. Enzymatic hydrolysis resulted in the maximal levels of glucose titer (220.7 g/L) and yield (73.5 %). L -lactic acid concentration reached to 204.1 g/L when SCB fermented with Lactobacillus casei ATCC 334 at a 25 % w/w solid loading. The two-step pretreatment SCB underwent morphological changes, as evidenced by FTIR, XRD, and SEM analyses. High cellulose levels and high lactic acid highlight the advantages on energy efficiency of a two-step combined pretreatment procedure over a standard single-step pretreatment technique.

Automated summary

An economical pretreatment method is needed to produce L-lactic acid from renewable biomass. The two-step combined pretreatment procedure showed advantages in energy efficiency over the standard single-step pretreatment technique, as demonstrated by six different combinatorial experiments.