Fast fluidization of dry acid pretreated wheat straw and consequent continuous bioconversions for l-lactic acid...

Materials flow of lignocellulose biomass in fluid form suitable for transportation in pumps and pipelines is prerequisite for continuous biorefinery process at industrial scale. A continuous process for l-lactic acid production was developed starting from fast fluidization of hot pretreated wheat straw solids into homogeneous and transportable slurry at moderate temperature, followed by continuous saccharification, biodetoxification, and fermentations. The final multi-stage continuous fermentation converted all the wheat straw derived sugars into 143.1 ± 0.9 g/L of l-lactic acid at the rate of 1.79 ± 0.01 g/L/h, the yield of 0.79 ± 0.01 g/g total sugars, and the chiral purity of 99.3% ± 0.1%. The performance using industrial wheat straw feedstock at a uniform dilution rate of 0.0375 h^-1 (residence time of ∼26.7 h), zero wastewater and toxin discharges was close to that of dry-mill process using corn feedstock. This study provided a prototype of completely continuous biorefining under high solids loading of lignocellulose utilization.