Method for synthesizing L-lactide from chiral L-lactic acid produced by using lignocellulose biomass as raw material

Abstract

The invention belongs to the field of biorefinery, and relates to a method for synthesizing L-lactide by producing chiral L-lactic acid from a lignocellulose raw material. The method comprises the following steps: (1) removing an inhibitor from a pretreated lignocellulose raw material in an ultimate biodegradation manner; (2) performing high-solid-content synchronous saccharification and co-fermentation on the lignocellulose raw material to obtain cellulose L-lactic acid with high concentration, high chirality and extremely low residual sugar; (3) preparing polymer grade L-lactic acid; and (4) carrying out dehydration, polycondensation, depolymerization and purification on the purified cellulose chiral L-lactic acid to obtain L-lactide. According to the method disclosed by the invention, the influence of an inhibitor on L-lactic acid fermentation and L-lactic acid purity is relieved by adopting a biodegradation method, high-concentration and extremely low-residual-sugar cellulose chiral L-lactic acid is obtained by adopting a high-solid-content total-sugar co-fermentation method, and the cellulose chiral L-lactic acid is subjected to the steps of purification, polycondensation, depolymerization and the like; the synthesis of the L-lactide from the lignocellulose raw material is realized.

Description

technical field [0001] The invention relates to the field of biorefinery, in particular to a research on the production of chiral L-lactic acid and the synthesis of L-lactide by using renewable resource lignocellulosic biomass raw materials. Background technique [0002] Polylactic acid (PLA) is a biodegradable plastic that has been widely used as a substitute for petroleum-derived polymers in packaging materials, biomedical materials, and other fields. The synthesis of polylactic acid is mainly achieved through a two-step method. First, chiral lactic acid monomers are polycondensed into low-molecular-weight polylactic acid, and then depolymerized to obtain lactide; then, lactide is used as a polymerization monomer to polymerize high-molecular-weight polylactic acid. The synthesis of lactide is the key step of polylactic acid. At present, lactide is mainly synthesized by using chiral lactic acid obtained by fermentation of starch raw materials, and its production cost and f...

AI Technical Summary

Problems solved by technology

The cellulose chiral L-lactic acid synthetic L-lactide that is produced with lignocellulose as raw material mainly has the following obstacles: (1) inhibitors (furfural, 5-hydroxymethylfurfural, vanilla aldehyde and syringaldehyde, etc.) will seriously inhibit the growth and lactic acid fermentation performance of fermentation strains, and the residual inhibitors make the purification of polymerization grade L-lactic acid very difficult; (2) cellulosic lactic acid fermentation strains account for 40% of total monosaccharides in lignocellulose % of non-glucose monosaccharides (xylose, arabinose, galactose and mannose, etc.) utilization rate is low, which not only leads to low yield and yield of cellulose lactic acid, but also the residual monosaccharides seriously affect the separation and separation of late stage polymerization grade lactic acid. purification

The above two key obstacles make it difficult to use chiral L-lactic acid synthesized from lignocellulosic biomass as a raw material for L-lactide synthesis

Images