Biotechnological production of enantiomerically pure d-lactic acid

Abstract

The fermentation process of l-lactic acid is well known. Little importance was attached to d-lactic acid, but in the past 10 years, d-lactic acid gained significantly in importance. d-Lactic acid is an interesting precursor for manufacturing heat-resistant polylactic acid (PLA) bioplastics which can be widely used, for example as packaging material, coatings, for textiles or in the automotive industry.This review provides a comprehensive overview of the most recent developments, including a spectrum of studied microorganisms and their capabilities for the production of d-lactic acid. Additionally, the technological achievements in biotechnological d-lactic acid production including fermentation techniques like fed batch, simultaneous saccharification, and fermentation and continuous techniques are presented. Attention is also turned to suitable alternative substrates and their applicability in fermentation processes. Furthermore, advantages and disadvantages of product recovery and purification are discussed. Economic aspects of PLA are pointed out, and the present industrial producers of lactic acid are briefly introduced.

Enhanced d‐lactic acid production by recombinant Saccharomyces cerevisiae following optimization of the global metabolic pathway

“…Recently, there has been a growing interest in bio‐based polymers produced from renewable feedstocks. One of the most promising bio‐based polymers is polylactic acid (PLA), which is already widely used as a packaging material (Klotz et al, ). Several forms of PLA can be synthesized by varying the ratio of l ‐ and d ‐isomers of lactic acid.…”

“…Owing to its superior thermal stability, scPLA has the potential to replace petroleum‐based polymers with many possible applications (Auras et al, ; Garlotta, ). PLLA has been the major form of PLA produced so far; thus, cost‐effective production of l ‐lactic acid, a monomer used for PLLA production, is well established compared to that of d ‐lactic acid, a monomer used for PDLA production, production process (Klotz et al, ). Therefore, a cost‐effective d ‐lactic acid production process is desired.…”

Microbial production of d‐lactic acid from dried distiller's grains with solubles

“…However, the hydrolysis of biomass materials, that are rich in cellulose/hemicellulose, produces a mixture of sugar monomers such as glucose, xylose, mannose, arabinose, and galactose. Several methods such as precipitation, extraction, crystallization, ion exchange, adsorption, membrane filtration, distillation, and nanofiltration can be used to recover lactic acid from fermentation broth [17,25]. and Sporolactobacillus sp.)…”

“…Over 90% of the commercially produced lactic acid is derived from microbial fermentation utilizing glucose, sucrose, or corn starch as carbon sources [13]. However, the relatively high cost of pure sugars has driven research on industrial fermentation towards the use of alternative resources, which can be obtained through the valorization of cheap, renewable agricultural biomass [13][14][15][16][17]. Apart from no interference with food industry, the other advantages of utilizing renewable sources is the possibility of producing cheaper fermentation medium at higher nutrient content to support bacterial growth.…”

“…Besides, fermentation broths derived from renewable sources also contain a mixture of compounds, including a variety of sugars and proteins, degraded compound from pretreatment, polyphenols and organic acids, and thus require an effective downstream processing for the recovery of the lactic acid [24,25]. Several methods such as precipitation, extraction, crystallization, ion exchange, adsorption, membrane filtration, distillation, and nanofiltration can be used to recover lactic acid from fermentation broth [17,25].…”