Background
There has been an increasing demand for optically pure d‐lactic and l‐lactic acid for the production of stereocomplex‐type polylactic acid. The d‐lactic acid production from ...lignocellulosic biomass is important owing to its great abundance in nature. Corn steep liquor (CSL) is a cheap nitrogen source used for industrial fermentation, though it contains a significant amount of l‐lactic acid, which decreases the optical purity of d‐lactic acid produced.
Method and results
To remove l‐lactic acid derived from the CSL‐based medium, l‐lactate oxidase (LoxL) from Enterococcus sp. NBRC 3427 was expressed in an engineered Lactiplantibacillus plantarum (formally called Lactobacillus plantarum) strain KOLP7, which exclusively produces d‐lactic acid from both hexose and pentose sugars. When the resulting strain was applied for d‐lactic acid fermentation from the mixed sugars consisting of the major constituent sugars of lignocellulose (35 g L–1 glucose, 10 g L–1 xylose, and 5 g L–1 arabinose) using the medium containing 10 g L–1 CSL, it completely removed l‐lactic acid derived from CSL (0.52 g L–1) and produced 41.7 g L–1 of d‐lactic acid. The l‐lactic acid concentration was below the detection limit, and improvement in the optical purity of d‐lactic acid was observed (from 98.2% to > 99.99%) by the overexpression of LoxL.
Conclusion and implications
The LoxL‐mediated consumption of l‐lactic acid would enable the production of optically pure d‐lactic acid in any medium contaminated by l‐lactic acid.
Graphical and Lay Summary
Corn steep liquor (CSL) is an inexpensive nitrogen source for fermentative production of lactic acid. However, it contains both l‐ and d‐lactic acids and reduces optical purity of lactic acid produced. In this study, l‐lactate oxidase from Enterococcus sp. NBRC 3427 (loxL) was expressed in Lactiplantibacillus plantarum KOLP7. The strain could successfully remove l‐lactic acid derived from CSL and produce optically pure d‐lactic acid (99.99%) from the mixture of glucose, and xylose, and arabinose, which are major components of lignocellulose hydrolysate.
Physical exercise can improve brain function and delay neurodegeneration; however, the initial signal from muscle to brain is unknown. Here we show that the lactate receptor (HCAR1) is highly ...enriched in pial fibroblast-like cells that line the vessels supplying blood to the brain, and in pericyte-like cells along intracerebral microvessels. Activation of HCAR1 enhances cerebral vascular endothelial growth factor A (VEGFA) and cerebral angiogenesis. High-intensity interval exercise (5 days weekly for 7 weeks), as well as L-lactate subcutaneous injection that leads to an increase in blood lactate levels similar to exercise, increases brain VEGFA protein and capillary density in wild-type mice, but not in knockout mice lacking HCAR1. In contrast, skeletal muscle shows no vascular HCAR1 expression and no HCAR1-dependent change in vascularization induced by exercise or lactate. Thus, we demonstrate that a substance released by exercising skeletal muscle induces supportive effects in brain through an identified receptor.
Once thought to be a waste product of anaerobic metabolism, lactate is now known to form continuously under aerobic conditions. Shuttling between producer and consumer cells fulfills at least three ...purposes for lactate: (1) a major energy source, (2) the major gluconeogenic precursor, and (3) a signaling molecule. “Lactate shuttle” (LS) concepts describe the roles of lactate in delivery of oxidative and gluconeogenic substrates as well as in cell signaling. In medicine, it has long been recognized that the elevation of blood lactate correlates with illness or injury severity. However, with lactate shuttle theory in mind, some clinicians are now appreciating lactatemia as a “strain” and not a “stress” biomarker. In fact, clinical studies are utilizing lactate to treat pro-inflammatory conditions and to deliver optimal fuel for working muscles in sports medicine. The above, as well as historic and recent studies of lactate metabolism and shuttling, are discussed in the following review.
Though originally thought of as a metabolic waste product and fatigue agent, lactate can now be regarded as the link between glycolytic and aerobic pathways. From its discovery to more recent clinical applications, Brooks provides a comprehensive look at lactate metabolism and shuttling in both basic physiology and medicine.
Polylactic acid is usually synthesized by ring-opening polymerization of lactide. And, lactide is prepared from lactic acid through polycondensation and depolymerization. Efficient production of ...lactic acid and lactide plays a positive role in promoting the rapid development of polylactic acid industry. This work sorts out recent progresses of the production of polylactic acid and its precursors (especially lactide) to clarify current research and discuss its future development direction.
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Poly(lactic acid) (PLA) plastics is of great significance to the sustainable development of the world. Today, most PLA is prepared by ring-opening polymerization of lactide (LT) synthesized from lactic acid (LA). The production capacity of high-quality LA is the basis for the production of PLA bioplastics. And, as the key intermediate for PLA synthesis, lactide (LT) also has a profound impact on the whole PLA industrial chain. The production capacity of LT is directly related to the application scale of PLA, and chemical purity and optical purity of LT significantly affect the properties of synthesized PLA. In this work, the research progresses on LA, LT, and PLA in recent years are sorted out to provide a comprehensively and systematic review. Apart from the introduction of the whole process of PLA production, this review highlights some of the latest methods with significant advantages in energy consumption, reaction integration, efficiency and yield in the production process.
A marketing study revealed that commercially available burger buns can contain up to 10% (w/w) of added sugar. In order to reduce sugar and maintaining the product quality at the same time, ...functional ingredients and alternative sweetening agents have to be incorporated. In this study, the sourdough lactic acid bacteria Leuconostoc citreum TR116, selected for its ability to produce high amounts of mannitol, was used to produce wheat sourdough and its biochemical characteristics (cell count, pH, TTA, sugar- and acid profile, as well as mannitol production) were monitored over 48 h. The so produced sourdough was then incorporated, as a functional ingredient, into a sugar reduced burger bun system and the quality characteristics of the dough and the final product were determined. Sourdough incorporation counteract the negative effects of sugar reduction on dough properties and resulted in the same viscoelastic properties (0.423 ± 0.008) and gluten-network-development (PMT: 160 ± 12.6 s; TM: 44.0 ± 2.6 BU) as the full-sugar control dough. Furthermore, the investigation of specific volume, crumb hardness and chewiness revealed no significant differences between sugar reduced sourdough burger buns and its control. It is noteworthy that sourdough contributed to browning reaction resulting in darker crumb and crust colour (−8.2%; −9.6%) and it extended microbial shelf life of the burger buns significantly (+3.5 days). Sensory evaluation showed no significant differences in sweetness and sourness between sugar reduced buns containing sourdough and the full-sugar control. In conclusion, the incorporation of mannitol-rich sourdough fermented by Leuconostoc citreum TR116 represents a novel technological approach in the field of sugar reduction and showed high potential as a functional ingredient to ameliorate the losses of important quality parameters. Especially sourdough containing higher amounts of mannitol and lower amounts of lactate improved significantly the dough and burger bun quality.
•Characterisation of Leuconostoc citreum in a sourdough system•Novel technological approach for sugar reduction•Natural production of mannitol in a sourdough system
Lactic acid (LA) is an important and versatile chemical that can be produced from renewable resources such as biomass. LA is used in the food, pharmaceutical, and polymers industries and is produced ...by microorganism fermentation; however, most microorganisms cannot directly utilize biomass such as starchy materials and cellulose. Here, we summarize LA production using several kinds of genetically modified microorganisms, such as LA bacteria, Escherichia coli, Corynebacterium glutamicum, and yeast. Using gene manipulation and metabolic engineering, the yield and optical purity of LA produced from biomass has been significantly improved. In this review, the drawbacks as well as improvements of LA production by fermentation is discussed.
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•Obtained 104.5g/L in l-lactic acid titer and 71.5% in overall yield by overcoming technical barriers.•Obtained minimum water consumption by dry milling biorefinery processing (DMBP) ...technology.•Developed Aspen plus model for l-lactic acid production from corn stover.•Better economic value of cellulosic l-lactic acid than cellulosic ethanol and starch l-lactic acid.
Technological potentials of l-lactic acid production from corn stover feedstock were investigated by experimental and techno-economic studies. An optimal performance with 104.5g/L in l-lactic acid titer and 71.5% in overall yield from cellulose in corn stover to l-lactic acid using an engineered Pediococcus acidilactici strain were obtained by overcoming several technical barriers. A rigorous Aspen plus model for l-lactic acid production starting from dry dilute acid pretreated and biodetoxified corn stover was developed. The techno-economic analysis shows that the minimum l-lactic acid selling price (MLSP) was $0.523perkg, which was close to that of the commercial l-lactic acid produced from starch feedstock, and 24% less expensive than that of ethanol from corn stover, even though the xylose utilization was not considered. The study provided a prototype of industrial application and an evaluation model for high titer l-lactic acid production from lignocellulose feedstock.
Lactic acid can synthesize high value-added chemicals such as poly lactic acid. In order to further minimize the cost of lactic acid production, some effective strategies (e.g., effective mutagenesis ...and metabolic engineering) have been applied to increase productive capacity of lactic acid bacteria. In addition, low-cost cheap raw materials (e.g., cheap carbon source and cheap nitrogen source) are also used to reduce the cost of lactic acid production. In this review, we summarized the recent developments in lactic acid production, including efficient strain modification technology (high-efficiency mutagenesis means, adaptive laboratory evolution, and metabolic engineering), the use of low-cost cheap raw materials, and also discussed the future prospects of this field, which could promote the development of lactic acid industry.
Lactic acid bacteria (LAB) constitute a heterogeneous group of microorganisms that produce lactic acid as the major product during the fermentation process. LAB are Gram-positive bacteria with great ...biotechnological potential in the food industry. They can produce bacteriocins, which are proteinaceous antimicrobial molecules with a diverse genetic origin, posttranslationally modified or not, that can help the producer organism to outcompete other bacterial species. In this review, we focus on the various types of bacteriocins that can be found in LAB and the organization and regulation of the gene clusters responsible for their production and biosynthesis, and consider the food applications of the prototype bacteriocins from LAB. Furthermore, we propose a revised classification of bacteriocins that can accommodate the increasing number of classes reported over the last years.
PLGA nanotherapeutics though representing a most promising platform for targeted cancer therapy are confronted with low stability and insufficient tumor cell uptake. Here, we report that hyaluronic ...acid (HA) coated PLGA nanoparticulate docetaxel (DTX-HPLGA) is particularly robust and can effectively target and suppress orthotopic human lung cancer. DTX-HPLGA was easily prepared with a small size of 154nm and negative surface charge of −22.7mV by nanoprecipitation and covalent coating with HA. DTX-HPLGA displayed a low IC50 of 0.91μg/mL in CD44+ A549 cells and a prolonged elimination half-life of 4.13h in nude mice. Interestingly, DTX-HPLGA demonstrated 4.4-fold higher accumulation in the cancerous lung than free DTX, reaching a remarkable level of 13.7%ID/g at 8h post-injection, in orthotopic human A549 lung cancer-bearing mice. Accordingly, DTX-HPLGA exhibited significantly better inhibition of tumor growth than free DTX, leading to healthy mice growth and markedly improved survival time. DTX-HPLGA with easy fabrication, excellent stability and tumor accumulation, effective tumor suppression, and low side effects is of particular interest for targeted chemotherapy of lung cancers.
Hyaluronic acid coating endows PLGA nanoparticulate docetaxel enhanced stability and superior tumor cell selectivity, leading to long circulation time, high drug accumulation in the cancerous lung, effective tumor inhibition and reduced systemic toxicity. Display omitted
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