Efficient Production of Optically Pure d -Lactic Acid from Raw Corn Starch by Using a Genetically Modified l -Lactate Dehydrogenase Gene-Deficient and α-Amylase-Secreting Lactobacillus plantarum Strain

Abstract

In order to achieve direct and efficient fermentation of optically pure D-lactic acid from raw corn starch, we constructed L-lactate dehydrogenase gene (ldhL1)-deficient Lactobacillus plantarum and introduced a plasmid encoding Streptococcus bovis 148 ␣-amylase (AmyA). The resulting strain produced only D-lactic acid from glucose and successfully expressed amyA. With the aid of secreting AmyA, direct D-lactic acid fermentation from raw corn starch was accomplished. After 48 h of fermentation, 73.2 g/liter of lactic acid was produced with a high yield (0.85 g per g of consumed sugar) and an optical purity of 99.6%. Moreover, a strain replacing the ldhL1 gene with an amyA-secreting expression cassette was constructed. Using this strain, direct D-lactic acid fermentation from raw corn starch was accomplished in the absence of selective pressure by antibiotics. This is the first report of direct D-lactic acid fermentation from raw starch.

Homo- d -Lactic Acid Fermentation from Arabinose by Redirection of the Phosphoketolase Pathway to the Pentose Phosphate Pathway in l -Lactate Dehydrogenase Gene-Deficient Lactobacillus plantarum

“…L. plantarum ⌬ldhL1 strain can produce optically pure D-lactic acid (12) from arabinose. However, this strain produces both D-lactic acid and acetic acid from arabinose.…”

Improved Production of Homo- d -Lactic Acid via Xylose Fermentation by Introduction of Xylose Assimilation Genes and Redirection of the Phosphoketolase Pathway to the Pentose Phosphate Pathway in l -Lactate Dehydrogenase Gene-Deficient Lactobacillus plantarum

“…Due to the presence of the PP pathway, IO-1 produces only L-lactic acid. We had previously disrupted the PK pathway by deletion of the phosphoketolase 1 gene (xpk1) in an L-lactate dehydrogenase gene (ldhL1)-deficient L. plantarum NCIMB 8826 strain which produces optically pure D-lactic acid (10) and introduced the PP pathway by introduction of the transketolase gene from Lactococcus lactis IL 1403 (tkt) into this strain. The resulting mutant, L. plantarum ⌬ldhL1-xpk1::tkt, successfully produces only lactic acid (exhibiting homo-lactic acid production) from arabinose that is metabolized via an intermediate compound, X5P (3), which is also an intermediate compound in xylose conversion (9).…”

“…The resulting plasmid was designated pGh9-⌬xpk2. Disruption of the xpk2 gene of L. plantarum ⌬ldhL1-xpk1::tkt (9) by using pGh9-⌬xpk2 was carried out by pG ϩ host plasmid-based double-crossover homologous integration, as described previously (10). The resulting xpk2 disruption strain of L. plantarum ⌬ldhL1-xpk1::tkt was designated L. plantarum ⌬ldhL1-xpk1::tkt-⌬xpk2.…”

Valorization of Agri-Food Waste via Fermentation: Production of l-lactic Acid as a Building Block for the Synthesis of Biopolymers

“…230 • C) that is approximately 50 • C higher than that of the respective single polymers [46]. Therefore, D-lactic acid, in addition to L-lactic acid, which has been the focus of production to date, is becoming increasingly important [47].…”