Recent advances in lactic acid production by microbial fermentation processes

Lactic acid production from lignocellulose-derived sugars using lactic acid bacteria: Overview and limits

Polymeric materials prepared from renewable natural resources are now being accepted as “bio-based polymers”, because they are superior to the conventional petroleum-based polymers in reducing the emission of carbon dioxide. Among them, poly(L-lactide) (PLLA) prepared by fermentation and polymerization is paid an immediate attention. Although PLLA exhibits a broad range of physico-chemical properties, its thermal and mechanical properties are somewhat poorer for use as ordinary structural materials. For improving these inferior properties, a stereocomplex form consisting of PLLA and its enantiomer poly(D-lactide) (PDLA) has high potential because of showing high melting nature (230 °C). It can be formed by simple polymer blend of PLLA and PDLA or more easily with stereoblock polylactides (sb-PLA) which are PLLA/PDLA block copolymers. These novel PLA polymers, named “Neo-PLA”, can provide a wide range of properties that have never be attained with single PLLA. Neo-PLA retains sustainability or bio-based nature, because both monomers L- and D-lactic acids are manufactured from starch by fermentation. Copyright © 2006 Society of Chemical Industry

Stereocomplexed polylactides (Neo-PLA) as high-performance bio-based polymers: their formation, properties, and application

In mineral salts medium under oxygen deprivation, Corynebacterium glutamicum exhibits high productivity of l-lactic acid accompanied with succinic and acetic acids. In taking advantage of this elevated productivity, C. glutamicum was genetically modified to produce d-lactic acid. The modification involved expression of fermentative d-lactate dehydrogenase (d-LDH)-encoding genes from Escherichia coli and Lactobacillus delbrueckii in l-lactate dehydrogenase (l-LDH)-encoding ldhA-null C. glutamicum mutants to yield strains C. glutamicum ΔldhA/pCRB201 and C. glutamicum ΔldhA/pCRB204, respectively. The productivity of C. glutamicum ΔldhA/pCRB204 was fivefold higher than that of C. glutamicum ΔldhA/pCRB201. By using C. glutamicum ΔldhA/pCRB204 cells packed to a high density in mineral salts medium, up to 1,336 mM (120 g l−1) of d-lactic acid of greater than 99.9% optical purity was produced within 30 h.

Production of d -lactic acid by Corynebacterium glutamicum under oxygen deprivation

Purification and characterization of cellulase produced by Bacillus amyoliquefaciens DL-3 utilizing rice hull.

Production of D-lactic acid from defatted rice bran by simultaneous saccharification and fermentation.

On the basis of growth rate at low pH, yield of lactic acid from glucose, and optical purity of lactic acid produced, we selected lactic acid bacteria favorable for production of optically pure L-lactic acid from defatted rice bran without sterilization. Of 21 strains tested, strains Nos. 13 and 16 produced 27-29kgm-3 of lactic acid with high optical purity from 100kgm-3 of unsterilized defatted rice bran in simultaneous saccharification and fermentation (SSF) with MRS medium at pH 4.5, a level at which the growth of indigenous lactic acid bacteria in defatted rice bran was suppressed. In a SSF process using strain No. 16 in which McIlvaine buffer (pH 4.5) was used instead of MRS medium, no growth of indigenous lactic acid bacteria was observed in defatted rice bran, and 28kgm-3 of lactic acid with 92% L-type content was produced from 100kgm-3 of unsterilized defatted rice bran. In SSF using McIlvaine buffer (pH 4.5), the protein fraction of defatted rice bran was found to play a significant role as a nitrogen source for the growth of lactic acid bacteria. By increasing the initial cell concentration to OD660=1.0 for SSF using strain No. 16 and McIlvaine buffer (pH 4.5), the proportion of L-lactic acid produced was enhanced to 95%.

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Production of L-Lactic Acid by Simultaneous Saccharification and Fermentation Using Unsterilized Defatted Rice Bran as a Carbon Source and Nutrient Components

Suguru Tanabe

Papers

Production of D-lactic acid from defatted rice bran by simultaneous saccharification and fermentation.

Production of L-Lactic Acid by Simultaneous Saccharification and Fermentation Using Unsterilized Defatted Rice Bran as a Carbon Source and Nutrient Components