Recent Advances in Lactic Acid Production by Lactic Acid Bacteria

The continuing significance of chiral agrochemicals

Chemical crop protection is one of the most cost-effective methods for agriculture, as crop failures can be prevented, and sustainable growth can be enabled regardless of the seasons. Agricultural production must be significantly increased in the future to meet the food needs of a growing world population. However, the continued loss of established active ingredients due to consumer perceptions, changing needs of farmers and ever-changing regulatory requirements is higher than annually new active ingredients introduced to the market. The development of innovative active ingredients is therefore essential to continuously improve the selectivity, efficacy and favorable environmental profile of agrochemicals. Molecules with stereogenic centers can be considered here, as they often have different properties than non-chiral molecules. Natural products and their congeners are still a valuable source of inspiration for chiral agrochemicals. However, only a few novel chiral agrochemicals are currently produced on an industrial scale as pure stereoisomers or in enriched form. As of 2018, around 43% of the 35 chiral products introduced to the market (herbicides, fungicides, insecticides, acaricides, and nematicides) contain one or more stereogenic centers in the molecule, and almost 69% of them have been marketed as racemic mixtures of enantiomers or stereoisomers. Surprisingly, the proportion of chiral agrochemicals is in the same order of magnitude as in the time frame from 2007 to 2017 with around 42%, respectively. This report therefore provides an overview of the continued importance of chiral agrochemicals brought to market in the last 6 years and describes the inherent related challenges of modern agrochemicals through the management of key aspects arising from innovative crop protection products. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Isolation and characterization of Schleiferilactobacillus harbinensis GX0002947 from naturally fermented sour porridge and its application in cereal fermentation

Sour porridge, a fermented food from the Guangxi Zhuang Autonomous Region of China, contains an abundance of lactic acid bacteria and has high nutritional value. In this study, a strain of Schleiferilactobacillus harbinensis GX0002947 was isolated from naturally fermented sour porridge from Fusui County, Chongzuo City, Guangxi Zhuang Autonomous Region of China. The strain was highly effective in the fermentation of sour porridge. It was found that strain S. harbinensis GX0002947 showed good acid and bile salt resistance at pH 3.5, bile salt concentration of 0.3 g/100 mL, in artificial gastrointestinal fluids, and the bacterial population density was greater than 106 CFU/mL. The fermentation broth and culture supernatant of strain S. harbinensis GX0002947 showed effective antibacterial activity against the foodborne pathogens Escherichia coli, Staphylococcus aureus, and Bacillus cereus. The optimum fermentation process for sour porridge was found to consist of a fermentation temperature of 37°C, inoculation dose of 12.5%, and fermentation time of 96 h, resulting in a total protein content of 397.33 μg/mL and a total amino acid content of 629.63 μmol/mL in the sour porridge. In addition, the community diversity of fermented sour porridge was explored by high-throughput Illumina sequencing. The results showed that fermentation of sour porridge by S. harbinensis GX0002947 resulted in the formation of a unique microbial community. Metabolites were compared between sour porridge fermented by strain S. harbinensis GX0002947 and naturally fermented sour porridge and were analyzed by LC-MS. This identified 24 differential metabolites which primarily included amino acids, carbohydrates, and lipids, suggesting that the associated pathways played a key role in the fermentation of sour porridge by S. harbinensis GX0002947. In conclusion, this study used inoculation of lactic acid bacteria for the fermentation of sour porridge, and assessed differences in microbial community structure and metabolites after inoculation with S. harbinensis GX0002947. These findings provided a theoretical basis and technical support for sour porridge production.

Advancements in metabolic engineering: unlocking the potential of key organic acids for sustainable industrial applications

This review explores the advancements, application potential, and challenges of microbial metabolic engineering strategies for sustainable organic acid production. By integrating gene editing, pathway reconstruction, and dynamic regulation, microbial platforms have achieved enhanced biosynthesis of key organic acids such as pyruvate, lactic acid, and succinic acid. Strategies including by-product pathway knockout, key enzyme overexpression, and improved CO2 fixation have contributed to higher production efficiency. Additionally, utilizing non-food biomass sources, such as lignocellulose, algal feedstocks, and industrial waste, has reduced reliance on conventional carbon sources, supporting sustainability goals. However, challenges remain in substrate inhibition, purification complexity, and metabolic flux imbalances. Addressing these requires omics-driven metabolic optimization, stress-resistant strain development, and biorefinery integration. Future research should focus on system-level design to enhance cost-effectiveness and sustainability, advancing industrial bio-manufacturing of organic acids.

Large-scale fermentation of Lactiplantibacillus pentosus 292 for the production of lactic acid and the storage strategy based on molasses as a preservative

BACKGROUND

Lactiplantibacillus pentosus 292 is a lactic acid bacterium (LAB) with significant probiotic potential, but large-scale production is often limited by high production costs and preservation challenges. This study aimed to develop a cost-effective medium to enhance lactic acid production and establish a feasible preservation strategy to support the strain's large-scale application.

RESULTS

A low-cost medium containing glucose, yeast powder, K₂HPO₄, and Tween-80 was formulated, enabling Lactiplantibacillus pentosus 292 to achieve a lactic acid yield of 16.24 g/L, representing an 83.48% increase compared to the traditional MRS medium. Fermentation kinetics models for bacterial growth, substrate consumption, and product generation were established in a 200-L fermenter using the Logistic, Luedeking-Piret-like, and Luedeking-Piret models, and the R2 values from the model equation were 0.9921 (OD600nm), 0.9942 (dry weight), 0.9506 (total protein), 0.8383 (lactic acid), 0.8898 (total sugar), and 0.8585 (reducing sugar), respectively, indicating that these models were suitable for accurately simulating the growth, nutrient production, and substrate consumption of L. pentosus 292. Additionally, a preservation strategy was developed by using 1-3% molasses as a preservative for the fermentation broth, and its efficacy was verified through temperature acceleration experiments.

CONCLUSION

In this work, a cost-effective medium that significantly increased lactic acid yield and a preservative based on molasses as a strategy to extend the storage period of fermentation products were developed for large-scale production of L. pentosus 292, a member of probiotic LAB. Additionally, large-scale fermentation kinetics models were constructed, providing valuable technical insights for the large-scale production and application of this LAB, highlighting its significant potential for industrial applications.

Advances and new horizons in metabolic engineering of heterotrophic bacteria and cyanobacteria for enhanced lactic acid production

Bacteria species such as E.Coli, Lactobacilli, and pediococci play an important role as starter strains in fermentation food or polysaccharides into lactic acid. These bacteria were metabolically engineered using multiple proven genome editing methods to enhance relevant phenotypes. The efficacy of these procedures varies depending on the editing tool used and researchers' ability to pick suitable recombinants, which significantly increased genome engineering throughput. Cyanobacteria produce oxygenic photosynthesis and play an important role in carbon dioxide fixing. The fixed carbon dioxide is then retained as polysaccharides in cells and metabolised into various low carbon molecules such as lactate, succinate, and ethanol. Lactate is used as a building ingredient in various bioplastics, food additives, and medicines. This review covers the recent advances in lactic acid production through metabolic and genetic engineering in bacteria and cyanobacteria.

Candida tropicalis, Clavispora lusitaniae, Limosilactobacillus fermentum, Liquorilactobacillus mali, and Leuconostoc pseudomesenteroides are associated with ethanol in Malian traditional fermented milk products

Fermented milk products (FMP) have been consumed by humans for millennia and the associated health benefits are no longer to be demonstrated. Although the manufacturing procedure have been industrialized, FMPs are still produced traditionally in many parts of the world with variable manufacturing procedures and unknown sanitary conditions. In this study, we aimed at comparing the physico-chemical properties of industrial and traditional FMPs from France and Mali as well as their microbial diversity. Therefore, 43 FMPs from France (seven yoghurts and four curdled milk products) and Mali (seven yoghurts, five curdled milk products, and 18 traditional fermented milk products) have been collected. These samples were analyzed using the culturomics approach, and GC-MS to quantify the ethanol concentration. Additionally, products pH and salinity were assessed. The results showed that more than half (56 %) of traditional and industrial FMPs contained ethanol (min = 0.05 % and max = 3.70 % Alcohol By Volume (ABV)), with a pH and salinity range (min = 4.43 and max = 5.80 and min = 0.10 and max = 1.80 %, respectively). Among them, 14 % exceed the threshold of 1.2 % ABV authorized by French regulations for non-alcoholic beverages. While only traditional FMPs from the "Nônô kumu" category presented a lower pH value than the other FMPs, all traditional FMPs had a higher salinity than industrial FMPs. Taxonomic analysis at the bacterial species level showed that Lactiplantibacillus plantarum was the dominant species isolated in Malian FMPs whereas Lactobacillus delbrueckii was the most frequent species in French FMPs. Moreover, Candida tropicalis, Candida lusitaniae, Limosilactobacillus fermentum, Leuconostoc pseudomesenteroides, and Liquorilactobacillus mali were significantly correlated with alcohol production. These results were confirmed using an in vitro experimental model. This study provides novel insights into bacterium-fungus interactions and ethanol production. Moreover, these results confirmed the link between specific yeasts and lactic acid bacteria in food and ethanol content, further supporting a recently identified putative role of these microbes in liver diseases.

Development of a Pre-Modification Strategy to Overcome Restriction-Modification Barriers and Enhance Genetic Engineering in Lactococcus lactis for Nisin Biosynthesis

Due to the barriers imposed by the restriction-modification (RM) system, Nisin-producing industrial strains of Lactococcus lactis often encounter low transformation efficiency, which seriously hinders the widespread application of genetic engineering in non-model L. lactis. Herein, we present a novel pre-modification strategy (PMS) coupled with optimized plasmid delivery systems designed to systematically evade RM barriers and substantially improve Nisin biosynthesis in L. lactis. Through the use of engineered Escherichia coli strains with methylation profiles specifically optimized for L. lactis C20, we have effectively evaded RM barriers, thereby facilitating the efficient introduction of large Nisin biosynthetic gene clusters into L. lactis. The PMS tools, which significantly improve the transformation efficiency (~103 transformants per microgram of DNA), have been further improved in combination with a Rolling Circle Amplification, resulting in a higher enhancement in transformation efficiency (~104 transformants per microgram of DNA). Using this strategy, large Nisin biosynthetic gene clusters and the expression regulation of all genes within the cluster were introduced and analyzed in L. lactis, leading to a highest Nisin titer of 11,052.9 IU/mL through a fed-batch fermentation in a 5 L bioreactor. This is the first systematic report on the expression regulation and application of a complete Nisin biosynthesis gene cluster in L. lactis. Taken together, our studies provide a versatile and efficient strategy for systematic evasion and enhancement of RM barriers and Nisin biosynthesis, thereby paving the way for genetic modification and metabolic engineering in L. lactis.

PanKB: An interactive microbial pangenome knowledgebase for research, biotechnological innovation, and knowledge mining

The exponential growth of microbial genome data presents unprecedented opportunities for unlocking the potential of microorganisms. The burgeoning field of pangenomics offers a framework for extracting insights from this big biological data. Recent advances in microbial pangenomic research have generated substantial data and literature, yielding valuable knowledge across diverse microbial species. PanKB (pankb.org), a knowledgebase designed for microbial pangenomics research and biotechnological applications, was built to capitalize on this wealth of information. PanKB currently includes 51 pangenomes from 8 industrially relevant microbial families, comprising 8402 genomes, over 500 000 genes and over 7M mutations. To describe this data, PanKB implements four main components: (1) Interactive pangenomic analytics to facilitate exploration, intuition, and potential discoveries; (2) Alleleomic analytics, a pangenomic-scale analysis of variants, providing insights into intra-species sequence variation and potential mutations for applications; (3) A global search function enabling broad and deep investigations across pangenomes to power research and bioengineering workflows; (4) A bibliome of 833 open-access pangenomic papers and an interface with an LLM that can answer in-depth questions using its knowledge. PanKB empowers researchers and bioengineers to harness the potential of microbial pangenomics and serves as a valuable resource bridging the gap between pangenomic data and practical applications.

Medical applications and prospects of polylactic acid materials

Polylactic acid (PLA) is a biodegradable and bio-based polymer that has gained significant attention as an environmentally friendly alternative to traditional petroleum-based plastics. In clinical treatment, biocompatible and non-toxic PLA materials enhance safety and reduce tissue reactions, while the biodegradability allows it to breakdown over time naturally, avoiding a second surgery. With the emergence of nanotechnology and three-dimensional (3D) printing, medical utilized-PLA has been produced with more structural and biological properties at both micro and macro scales for clinical therapy. This review summarizes current applications of the PLA-based biomaterials in drug delivery systems, orthopedic treatment, tissue regenerative engineering, and surgery and medical devices, providing viewpoints regarding the prospective medical utilization.

Innovative Lactic Acid Production Techniques Driving Advances in Silage Fermentation

Lactic acid (LA) plays a crucial role in the silage process, which occurs through LA fermentation. Consequently, there is a strong correlation between lactic acid production and the efficiency of the silage. However, traditional methods face challenges like long fermentation times, low acid production, and unstable quality, limiting agricultural preservation. This paper aims to explore innovations in lactic acid production technologies and show how these technologies have driven the development of silage fermentation for agricultural conservation. First, the important role of LA in agricultural preservation and the limitations of traditional silage techniques are presented. Next, advancements in LA production methods are thoroughly examined, covering the selection of microbial strains and the substitution of fermentation substrates. Following this, new technologies for silage fermentation are explored, drawing from innovations in LA production. These include the selection of LA strains, optimization of fermentation conditions, and improvements in fermentation techniques. These innovations have proven effective in increasing LA production, improving feed quality, extending shelf life, and providing new solutions to enhance agricultural production and sustainability.

Rapid and accurate quantification of viable Bifidobacterium cells in milk powder with a propidium monoazide-antibiotic fluorescence in situ hybridization-flow cytometry method

Due to its beneficial effects on human health, Bifidobacterium is commonly added to milk powder. Accurate quantification of viable Bifidobacterium is essential for assessing the therapeutic efficacy of milk powder. In this study, we introduced a novel propidium monoazide (PMA)-antibiotic fluorescence in situ hybridization (AFISH)-flow cytometry (FC) method to rapidly and accurately quantify viable Bifidobacterium cells in milk powder. Briefly, Bifidobacterium cells were treated with chloramphenicol (CM) to increase their rRNA content, followed by staining with RNA-binding oligonucleotide probes, based on the AFISH technique. Then, the DNA-binding dye PMA was used to differentiate between viable and nonviable cells. The PMA-AFISH-FC method, including sample pretreatment, CM treatment, dual staining, and FC analysis, required approximately 2 h and was found to be better than the current methods. This is the first study to implement FC combined with PMA and an oligonucleotide probe for detecting Bifidobacterium.

Lactic acid production by Lactobacillus casei using a sequence of seasonally available fruit wastes as sustainable carbon sources

Introduction: Lactic acid (LA) production from fossil resources is unsustainable owing to their depletion and environmental concerns. Thus, this study aimed to optimize the production of LA by Lactobacillus casei in a cultured medium containing fruit wastes (FWs) from agro-industries and second cheese whey (SCW) from dairy production, supplemented with maize steep liquor (MSL, 10% v/v) as the nitrogen source. Methods: The FWs were selected based on seasonal availability [early summer (early ripening peach), full summer (melon), late summer (pear), and early autumn (apple)] and SCW as annual waste. Small-scale preliminary tests as well as controlled fermenter experiments were performed to demonstrate the potential of using various food wastes as substrates for LA fermentation, except for apple pomace. Results and discussion: A 5-cycle repeated batch fermentation was conducted to optimize waste utilization and production, resulting in a total of 180.56 g/L of LA with a volumetric productivity of 0.88 g/L∙h. Subsequently, mechanical filtration and enzymatic hydrolysis were attempted. The total amount of LA produced in the 5-cycle repeated batch process was 397.1 g/L over 288 h, achieving a volumetric productivity of 1.32 g/L∙h. These findings suggest a promising biorefinery process for low-cost LA production from agri-food wastes.

Biosensor-assisted CRISPRi high-throughput screening to identify genetic targets in Zymomonas mobilis for high d-lactate production

Lactate is an important monomer for the synthesis of poly-lactate (PLA), which is a substitute for the petrochemical plastics. To achieve the goal of high lactate titer, rate, and yield for commercial production, efficient lactate production pathway is needed as well as genetic targets that affect high lactate production and tolerance. In this study, an LldR-based d-lactate biosensor with a broad dynamic range was first applied into Zymomonas mobilis to select mutant strains with strong GFP fluorescence, which could be the mutant strains with increased d-lactate production. Then, LldR-based d-lactate biosensor was combined with a genome-wide CRISPR interference (CRISPRi) library targeting the entire genome to generate thousands of mutants with gRNA targeting different genetic targets across the whole genome. Specifically, two mutant libraries were selected containing 105 and 104 mutants with different interference sites from two rounds of fluorescence-activated cell sorting (FACS), respectively. Two genetic targets of ZMO1323 and ZMO1530 were characterized and confirmed to be associated with the increased d-lactate production, further knockout of ZMO1323 and ZMO1530 resulted in a 15% and 21% increase of d-lactate production, respectively. This work thus not only established a high-throughput approach that combines genome-scale CRISPRi and biosensor-assisted screening to identify genetic targets associated with d-lactate production in Z. mobilis, but also provided a feasible high-throughput screening approach for rapid identification of genetic targets associated with strain performance for other industrial microorganisms.

Succession of microbiota and its influence on the dynamics of volatile compounds in the semi-artificial inoculation fermentation of mulberry wine

To improve the delightful flavor of mulberry wine through semi-artificial inoculation fermentation with Saccharomyces cerevisiae, we studied the dynamics change of microbiota, along with the physicochemical properties and metabolite profiles and their interaction relationship during the fermentation process. The abundance of lactic acid bacteria (Weissella, Lactobacillus, Fructobacillus, and Pediococcus) increased significantly during fermentation, while yeasts gradually established dominance. The inter-kingdom network of the dominant genera analysis further identified the following as core microbiota: Alternaria, Botrytis, Kazachstania, Acremonium, Mycosphaerella, Pediococcus, Gardnerella, and Schizothecium. Additionally, pH, alcohol, and total acid were significantly affected by microbiota variation. Fourteen of all identified volatile compounds with key different aromas were screened using PCA, OPLS-DA, and rOAV. The network of interconnected core microbiota with key different aromas revealed that Kazachstania and Pediococcus had stronger correlations with 1-butanol, 3-methyl-, propanoic acid, and 2-methyl-ethyl ester.

The potentials and challenges of using fermentation to improve the sensory quality of plant-based meat analogs

Despite the advancements made in improving the quality of plant-based meat substitutes, more work needs to be done to match the texture, appearance, and flavor of real meat. This review aims to cover the sensory quality constraints of plant-based meat analogs and provides fermentation as a sustainable approach to push these boundaries. Plant-based meat analogs have been observed to have weak and soft textural quality, poor mouth feel, an unstable color, and unpleasant and beany flavors in some cases, necessitating the search for efficient novel technologies. A wide range of microorganisms, including bacteria such as Lactobacillus acidophilus and Lactiplantibacillus plantarum, as well as fungi like Fusarium venenatum and Neurospora intermedia, have improved the product texture to mimic fibrous meat structures. Additionally, the chewiness and hardness of the resulting meat analogs have been further improved through the use of Bacillus subtilis. However, excessive fermentation may result in a decrease in the final product's firmness and produce a slimy texture. Similarly, several microbial metabolites can mimic the color and flavor of meat, with some concerns. It appears that fermentation is a promising approach to modulating the sensory profiles of plant-derived meat ingredients without adverse consequences. In addition, the technology of starter cultures can be optimized and introduced as a new strategy to enhance the organoleptic properties of plant-based meat while still meeting the needs of an expanding and sustainable economy.

The biochemical characteristics of viable but nonculturable state Yersinia enterocolitica induced by lactic acid stress and its presence in food systems

The viable but nonculturable (VBNC) state is adopted by many foodborne pathogenic bacteria to survive in adverse conditions. This study found that lactic acid, a widely used food preservative, can induce Yersinia enterocolitica to enter a VBNC state. Y. enterocolitica treated with 2 mg/mL lactic acid completely lost culturability within 20 min, and 10.137 ± 1.693 % of the cells entered a VBNC state. VBNC state cells could be recovered (resuscitated) in tryptic soy broth (TSB), 5 % (v/v) Tween80-TSB, and 2 mg/mL sodium pyruvate-TSB. In the VBNC state of Y. enterocolitica induced by lactic acid, the intracellular adenosine triphosphate (ATP) concentration and various enzyme activities were decreased, and the reactive oxygen species (ROS) level was elevated, compared with uninduced cells. The VBNC state cells were significantly more resistant to heat and simulated gastric fluid than uninduced cells, but their ability to survive in a high-osmotic-pressure environment was significantly less than that of uninduced cells. The VBNC state cells induced by lactic acid changed from long rod-like to short rod-like, with small vacuoles at the cell edges; the genetic material was loosened and the density of cytoplasm was increased. The VBNC state cells had decreased ability to adhere to and invade Caco-2 (human colorectal adenocarcinoma) cells. The transcription levels of genes related to adhesion, invasion, motility, and resistance to adverse environmental stress were downregulated in VBNC state cells relative to uninduced cells. In meat-based broth, all nine tested strains of Y. enterocolitica entered the VBNC state after lactic acid treatment; among these strains, only VBNC state cells of Y. enterocolitica CMCC 52207 and Isolate 36 could not be recovered. Therefore, this study is a wake-up call for food safety problems caused by VBNC state pathogens induced by lactic acid.

Integrated lactic acid production from lignocellulosic agricultural wastes under thermal conditions

The production of lactic acid (LA) from agricultural wastes attracts great attention because of the sustainability and abundance of lignocellulosic feedstocks, as well as the increasing demand for biodegradable polylactic acid. In this study, we isolated a thermophilic strain Geobacillus stearothermophilus 2H-3 for use in robust production of L-(+)LA under the optimal conditions of 60 °C, pH 6.5, which were consistent with the whole-cell-based consolidated bio-saccharification (CBS) process. Sugar-rich CBS hydrolysates derived from various agricultural wastes, including corn stover, corncob residue, and wheat straw, were used as the carbon sources for 2H-3 fermentation by directly inoculating 2H-3 cells into the CBS system, without intermediate sterilization, nutrient supplementation, or adjustment of fermentation conditions. Thus, we successfully combined two whole-cell-based steps into a one-pot successive fermentation process to efficiently produce LA with high optical purity (99.5%), titer (51.36 g/L), and yield (0.74 g/g_biomass). This study provides a promising strategy for LA production from lignocellulose through CBS and 2H-3 fermentation integration.

Deletion of QDR genes in a bioethanol-producing yeast strain reduces propagation of contaminating lactic acid bacteria

Bacterial contaminations in yeast fermentation tanks are a recurring problem for the bioethanol production industry. Lactic acid bacteria (LAB), particularly of the genus Lactobacillus, are the most common contaminants. Their proliferation can reduce fermentation efficiency or even impose premature shutdown for cleaning. We have previously reported that laboratory yeast strains naturally excrete amino acids via transporters of the Drug: H⁺ Antiporter-1 (DHA1) family. This excretion allows yeast to cross-feed LAB, which are most often unable to grow without an external amino acid supply. Whether industrial yeast strains used in bioethanol production likewise promote LAB proliferation through cross-feeding has not been investigated. In this study, we first show that the yeast strain Ethanol Red used in ethanol production supports growth of Lactobacillus fermentum in an amino-acid-free synthetic medium. This effect was markedly reduced upon homozygous deletion of the QDR3 gene encoding a DHA1-family amino acid exporter. We further show that cultivation of Ethanol Red in a nonsterile sugarcane-molasses-based medium is associated with an increase in lactic acid due to LAB growth. When Ethanol Red lacked the QDR1, QDR2, and QDR3 genes, this lactic acid production was not observed and ethanol production was not significantly reduced. Our results indicate that Ethanol Red cultivated in synthetic or molasses medium sustains LAB proliferation in a manner that depends on its ability to excrete amino acids via Qdr transporters. They further suggest that using mutant industrial yeast derivatives lacking DHA1-family amino acid exporters may be a way to reduce the risk of bacterial contaminations during fermentation.

Engineering Microorganisms to Produce Bio-Based Monomers: Progress and Challenges

Bioplastics are polymers made from sustainable bio-based feedstocks. While the potential of producing bio-based monomers in microbes has been investigated for decades, their economic feasibility is still unsatisfactory compared with petroleum-derived methods. To improve the overall synthetic efficiency of microbial cell factories, three main strategies were summarized in this review: firstly, implementing approaches to improve the microbial utilization ability of cheap and abundant substrates; secondly, developing methods at enzymes, pathway, and cellular levels to enhance microbial production performance; thirdly, building technologies to enhance microbial pH, osmotic, and metabolites stress tolerance. Moreover, the challenges of, and some perspectives on, exploiting microorganisms as efficient cell factories for producing bio-based monomers are also discussed.

Improving the Utilization of Food Waste: Conversion of Food Waste into Residual Food Dried Substance and Use of This Material as a Culture Nutrient for Microbial Production of Lactic Acid

To reduce food waste (FW) disposal costs, many Koreans now convert FW into residual food dried substances (RFDS) using a house-service food drying machine and then dispose of the RFDS. To recycle RFDS, we tested whether RFDS could be used as a culture nutrient to produce value-added microbial chemicals. As a case study, we attempted to produce lactic acid (LA) by cultivating lactic acid bacteria using RFDS. To prepare the culture medium for LA production, we finely ground the RFDS and dissolved it with CaCO₃, a pH-controlling agent. Six lactic acid bacteria were tested to improve LA production, with Lactococcus lactis showing the highest LA production. To enhance LA production, three hydrolytic enzymes, amylase, protease, and lipase, were introduced separately or simultaneously into the RFDS medium during the cultivation of the L. lactis strain. The addition of amylase alone was the most effective in increasing LA production. We then investigated the effect of the RFDS concentration on LA production. The highest LA production was achieved when 100 g/L of RFDS was used. LA production was scaled up using a 5 L bioreactor. During the fermentation, LA production improved to 46.32 g/L, which was 1.73-fold higher than that (26.83 g/L) obtained from the flask culture. These results show that RFDS from FW can be used as a culture nutrient to produce LA. Our study provides a new and simple FW recycling method and lays the foundation for expanding the usability of FW.

Bioconversion of biowaste into renewable energy and resources: A sustainable strategy

Due to its high amount of organic and biodegradable components that can be recycled, biowaste is not only a major cause of environmental contamination, but also a vast store of useful materials. The transformation of biowaste into energy and resources via biorefinery is an unavoidable trend, which could aid in reducing carbon emissions and alleviating the energy crisis in light of dwindling energy supplies and mounting environmental difficulties related with solid waste. In addition, the current pandemic and the difficult worldwide situation, with their effects on the economic, social, and environmental aspects of human life, have offered an opportunity to promote the transition to greener energy and sources. In this context, the current advancements and possible trends of utilizing widely available biowaste to produce key biofuels (such as biogas and biodiesel) and resources (such as organic acid, biodegradable plastic, protein product, biopesticide, bioflocculant, and compost) are studied in this review. To achieve the goal of circular bioeconomy, it is necessary to turn biowaste into high-value energy and resources utilizing biological processes. In addition, the usage of recycling technologies and the incorporation of bioconversion to enhance process performance are analyzed critically. Lastly, this work seeks to reduce a number of enduring obstacles to the recycling of biowaste for future use in the circular economy. Although it could alleviate the global energy issue, additional study, market analysis, and finance are necessary to commercialize alternative products and promote their future use. Utilization of biowaste should incorporate a comprehensive approach and a methodical style of thinking, which can facilitate product enhancement and decision optimization through multidisciplinary integration and data-driven techniques.

Characterization, High-Density Fermentation, and the Production of a Directed Vat Set Starter of Lactobacilli Used in the Food Industry: A Review

Lactobacilli have been widely concerned for decades. Bacteria of the genus Lactobacillus have been commonly employed in fermented food to improve the appearance, smell, and taste of food or prolong its shelf-life. They comprise 261 species (by March 2020) that are highly diverse at the phenotypic, ecological, and genotypic levels. Some Lactobacilli strains have been documented to be essential probiotics, which are defined as a group of living microorganisms that are beneficial to the health of the host when ingested in sufficiency. However, the characterization, high-density fermentation, and the production of a directed vat set (DVS) starter of Lactobacilli strains used in the food industry have not been systematically reported. This paper mainly focuses on reviewing Lactobacilli as functional starter cultures in the food industry, including different molecular techniques for identification at the species and strain levels, methods for evaluating Lactobacilli properties, enhancing their performance and improving the cell density of Lactobacilli, and the production techniques of DVS starter of Lactobacilli strains. Moreover, this review further discussed the existing problems and future development prospects of Lactobacilli in the food industry. The viability and stability of Lactobacilli in the food industry and gastrointestinal environment are critical challenges at the industrial scale. The new production equipment and technology of DVS starter of Lactobacilli strains will have the potential for large-scale application, for example, developing low-temperature spray drying, freezing granulation drying, and spray freeze-drying.

The control of Fusarium growth and decontamination of produced mycotoxins by lactic acid bacteria

Global crop and food contamination with mycotoxins are one of the primary worldwide concerns, while there are several restrictions regarding approaching conventional physical and chemical mycotoxins decontamination methods due to nutrition loss, sensory attribute reduction in foods, chemical residual, inconvenient operation, high cost of equipment, and high energy consumption of some methods. In this regard, the overarching challenges of mycotoxin contamination in food and food crops require the development of biological decontamination strategies. Using certain lactic acid bacteria (LAB) as generally recognized safe (GRAS) compounds is one of the most effective alternatives due to their potential to release antifungal metabolites against various fungal factors species. This review highlights the potential applications of LAB as biodetoxificant agents and summarizes their decontamination activities against Fusarium growth and Fusarium mycotoxins released into food/feed. Firstly, the occurrence of Fusarium and the instrumental and bioanalytical methods for the analysis of mycotoxins were in-depth discussed. Upgraded knowledge on the biosynthesis pathway of mycotoxins produced by Fusarium offers new insightful ideas clarifying the function of these secondary metabolites. Moreover, the characterization of LAB metabolites and their impact on the decontamination of the mycotoxin from Fusarium, besides the main mechanisms of mycotoxin decontamination, are covered. While the thematic growth inhibition of Fusarium and decontamination of their mycotoxin by LAB is very complex, approaching certain lactic acid bacteria (LAB) is worth deeper investigations.

State of the Art on the Microbial Production of Industrially Relevant Organic Acids

The industrial relevance of organic acids is high; because of their chemical properties, they can be used as building blocks as well as single-molecule agents with a huge annual market. Organic acid chemical platforms can derive from fossil sources by petrochemical refining processes, but most of them also represent natural metabolites produced by many cells. They are the products, by-products or co-products of many primary metabolic processes of microbial cells. Thanks to the potential of microbial cell factories and to the development of industrial biotechnology, from the last decades of the previous century, the microbial-based production of these molecules has started to approach the market. This was possible because of a joint effort of microbial biotechnologists and biochemical and process engineers that boosted natural production up to the titer, yield and productivity needed to be industrially competitive. More recently, the possibility to utilize renewable residual biomasses as feedstock not only for biofuels, but also for organic acids production is further augmenting the sustainability of their production, in a logic of circular bioeconomy. In this review, we briefly present the latest updates regarding the production of some industrially relevant organic acids (citric fumaric, itaconic, lactic and succinic acid), discussing the challenges and possible future developments of successful production.

Examining organic acid production potential and growth-coupled strategies in Issatchenkia orientalis using constraint-based modeling

Growth-coupling product formation can facilitate strain stability by aligning industrial objectives with biological fitness. Organic acids make up many building block chemicals that can be produced from sugars obtainable from renewable biomass. Issatchenkia orientalis is a yeast strain tolerant to acidic conditions and is thus a promising host for industrial production of organic acids. Here, we use constraint-based methods to assess the potential of computationally designing growth-coupled production strains for I. orientalis that produce 22 different organic acids under aerobic or microaerobic conditions. We explore native and engineered pathways using glucose or xylose as the carbon substrates as proxy constituents of hydrolyzed biomass. We identified growth-coupled production strategies for 37 of the substrate-product pairs, with 15 pairs achieving production for any growth rate. We systematically assess the strain design solutions and categorize the underlying principles involved.