Plantarum Fermentation Research Articles

Effect of Sprouting, Fermentation and Cooking on Antioxidant Content and Total Antioxidant Activity in Quinoa and Amaranth.

The study of different processing techniques, such as sprouting, cooking and fermentation, can help to develop new products for human health. In this work, raw, cooked and fermented seeds and germinated seeds of Chenopodium quinoa Willd. var. Tunkahuan and Amaranthus caudatus L. var. Alegrìa were compared for the content of antioxidant molecules, total antioxidant capacity and mineral elements. Fermentation was induced spontaneously, with the yeast Saccharomyces cerevisiae, with the bacterium Lactobacillus plantarum and with both microorganisms, for 24 and 48 h. The increase in antioxidant molecules and antioxidant activity was induced by germination, by 24 h of spontaneous fermentation (polyphenols and flavonoids) and by 24 h of L. plantarum fermentation (total antioxidant activity) for both species. Germinated seeds of the two plants showed higher values in respect to seeds of macroelements and microelements. No genotoxic but rather protective effects were determined for seed and germinated seed extracts using the D7 strain of S. cerevisiae, a good tool for the evaluation of protection from oxidative damage induced by radical oxygen species (ROS) in cells and tissues. Therefore, the two varieties could be very suitable for their use in human diet and in supplements, especially as germinated seeds or as fermented foods.

Quality of fermented pumpkin beverages under different fermentation conditions by Lactobacillus plantarumFNCC 020

SummaryDevelopment of health‐promoting natural products has received importance, and fermented pumpkin can be a viable option, mainly regarding its carotenoid contents. This study aimed to investigate the quality of fermented pumpkin beverages (FPB) under various fermentation conditions (control, T1 = 30 °C, 12 h; T2 = 30 °C, 18 h; T3 = 30 °C, 24 h; T4 = 40 °C, 12 h; T5 = 40 °C, 18 h; T6 = 40 °C, 24 h) by Lactobacillus plantarum. Cell count of lactic acid bacteria, pH, chemical quality (soluble solid, acidity, total sugar, total phenolic content, total flavonoid content, and antioxidant activity), carotenoid contents, and colour attributes (h*, chroma, L*, and yellowing index) of FPB samples were studied. As a result, LAB fermentation significantly affected acidity and total sugar of FPB samples, while it did not change pH and soluble solids significantly. Besides, carotenoid contents and colour attributes of FPB were not different during fermentation, indicating that L. plantarum fermentation retained carotenoids and maintained physical appearances. Regarding sugars and organic acids, their quantity changed due to fermentation and lactic acids increased greatly up to three times higher than control after 24 h of fermentation at 30 °C. Moreover, fermentation by L. plantarum improved total phenolic content, total flavonoid content, and antioxidant activity, and these may recommend FPB as a potential functional product.

The effect of Lactiplantibacillus plantarum fermentation and blanching on microbial population, nutrients, anti-nutrients and antioxidant properties of fresh and dried mature Moringa oleifera leaves

Moringa oleifera is an excellent source of nutrients and functional ingredients of human health significance. This study was conducted to determine the role of lactic acid fermentation and blanching in improving nutritional attributes and functional properties of M. oleifera leaves. Submerged lactic acid fermentation of M. oleifera was carried out for 24 h by using a Lactiplantibacillus plantarum strain. The results showed that fermentation resulted in a microbial population of M. oleifera leaves dominated with higher count of L. plantarum i.e., 4.06 log10 CFU/g after 24 h fermentation. L. plantarum count was reduced from 4.06 to 1.61 log10 CFU/g in fermented M.oleifera leaves powder after cabinet dehydration. Higher levels of protein (29.87 %), and fiber (32.26 %) were observed in fermented M. oleifera leaves while the levels of carbohydrates (10.74 %), fat (7.72 %), and energy (232.06 kcal) were lower than the levels observed in raw and blanched leaves. Lactic acid fermentation also anticipated reduction in anthocyanin (14.50–10.37 mg/100g), chlorophyll A (52.64–45.35 mg/100g), and lycopene (11.94–9.13 mg/100g) content of M. oleifera leaves. Fermentation significantly (p ≤ 0.05) increased level of total phenolic content i.e., 55.48 mg gallic acid equivalents (GAE)/g, total flavonoid contents i.e., 70.81 mg quercetin equivalent (QE)/g and flavonols i.e., 36.97 mg QE/g. Lactic acid fermentation reduced the levels of intrinsic nutrient inhibitors such as alkaloids (2.74–1.94 g/100g; 29 % ↓), saponins (3.80–2.98 g/100g: 20 % ↓), oxalates (2.43–1.85 g/100g; 24 % ↓), tannin (0.83–0.44 g/100g; 47 % ↓), and phytic acid (1.94–1.02 g/100g; 47 % ↓) compared with the raw leaves. The results suggest lactic acid fermentation is a cost-effective technique to improve nutritional and health perspectives of M. oleifera leaves.

Effect of cellulase and pentosanase with lactic acid bacteria to increase gluten formation and elasticity in whole-wheat dough sheets

Whole-wheat flour (WWF) is highly nutritious. However, bran hinders the development of the gluten network and affects the quality properties of whole-wheat products. Lactic acid bacteria (LAB) and cellulase and pentosanase (Cel/Pn) were used to ferment whole-wheat dough sheets (WWDSs) containing bran with varying particle sizes. The effects of enzyme (Cel/Pn)-assisted Lactobacillus brevis (Lbr) and L. plantarum (Lpl) fermentation on the structural and rheological properties of WWDSs were explored. With decreasing bran particle size (BPS), the glutenin macropolymer (GMP) contents of control, Lbr-Cel/Pn- and Lpl-Cel/Pn-treated sheets increased from 3.66, 1.78 and 1.79 mg/g to 4.29, 3.01 and 3.06 mg/g, respectively. The –SH contents of Lbr-Cel/Pn- and Lpl-Cel/Pn-treated dough sheets with BPS <100 μm decreased by 0.38 and 0.37 μmol/L, respectively, and the extension distance of the Lpl-Cel/Pn-treated sheet increased by 52%. After dual enzyme/bacteria treatment, a more stable microstructure was observed in the dough sheet containing finer bran particles. The dual treatment effectively reduced bran-induced damage to the wheat gluten network. Thus, the dual treatment used in this study could potentially be used to improve the quality of whole-wheat products.

Bioactive compounds, volatile compounds, rheological properties and bacteriostatic activities of fig juices with oligosaccharides supplementation fermented by Lactiplantibacillus plantarum

The objective of this study was to investigate the effects of Lactiplantibacillus plantarum fermentation on the bioactive compounds, volatile compounds, rheological properties and bacteriostatic activities of fig juices supplemented with oligosaccharides, namely fructooligosaccharides (FOS), galactooligosaccharides (GOS), isomaltooligosaccharides (IMO), xylooligosaccharides (XOS), stachyose (SOE) and mannanoligosaccharides (MOS). Results showed that SOE, FOS and IMO supplementations stimulated the proliferation of Lactiplantibacillus plantarum, especially for SOE, exhibiting the highest viable bacterial counts (9.84 log CFU/mL). Oligosaccharides supplementation accelerated the conversion of carbohydrates to organic acids, and increased the total contents of flavonoid (TFC) and carotenoid (TCC) during fermentation, of which FOS exhibited the greatest increases in TFC (66.28 mg RE/L) and TCC (0.032 mg/L). Furthermore, the highest levels of DPPH RSA (65.88%) and ABTS RSA (66.24%) were found in fermented fig juice supplemented with MOS, while the highest level of FRAP (0.97 mmol Trolox/L) and protocatechuic acid (6.97 mg/L) was observed in that with GOS. The total contents of alcohols and esters were significantly increased, while aldehyde content was decreased by oligosaccharides supplementation. In addition, oligosaccharides supplementation decreased the apparent viscosity of fermented juices. Fermented juices supplemented with FOS exhibited dramatically effective inhibition against Escherichia coli, Staphylococcus aureus and Listeria monocytogenes, due to the ruptures of cell surfaces and collapse of cellular structure. According to Pearson's correlation analysis, protocatechuic acid content was significantly and positively correlated with bacteriostatic activities. It was suggested that FOS should be a better probiotic additive for the preparation of fermented fig juice.

Effects of Physicochemical and Biological Treatment on Structure, Functional and Prebiotic Properties of Dietary Fiber from Corn Straw.

Corn straw is one kind of agricultural by-product containing 70-80% insoluble dietary fiber (IDF). In order to develop corn straw dietary fiber, this study was conducted to increase soluble dietary fiber (SDF) yield and improve the structure, functional and prebiotic properties of IDF and SDF from corn straw treated by alkali oxidation treatment, enzymatic hydrolysis, microbial fermentation and the combination of these methods. The results demonstrated that the yield of SDF was significantly increased from 2.64% to 17.15% after corn straw was treated by alkali oxidation treatment + Aspergillus niger fermentation + cellulase hydrolysis, compared with untreated corn straw. The SDF extracted from corn straw treated by alkali oxidation treatment + Aspergillus niger fermentation + cellulase hydrolysis (F-SDF) exhibited a honeycomb structure, low crystallinity (11.97%), good antioxidant capacity and high capacities of water holding, water solubility and cholesterol absorption and promoted short-chain fatty acids production by chicken cecal microbial fermentation in vitro. F-SDF enhanced the antibacterial activity against Escherichia coli and Staphylococcus aureus proliferations of Lactobacillus plantarum when it was used as a substrate for Lactobacillus plantarum fermentation. It could be concluded that the combined treatments could increase SDF yield from corn straw and improve its functional and prebiotic properties.

Effects of Lactobacillus plantarum fermentation on the structure, physicochemical properties, and digestibility of foxtail millet starches

This study investigated the effects of Lactobacillus plantarum fermentation on the structural, physicochemical, and digestive properties of foxtail millet starches. The fermented starch granules formed a structure with honeycomb-like dents, uneven pores, and reduced particle size. As the fermentation time extended, the amylose content of waxy (0.88 %) and non-waxy (33.71 %) foxtail millet starches decreased to the minimum value at 24 h (0.59 % and 29.19 %, respectively), and then increased to 0.85 % and 31.87 % at 72 h, respectively. Both native and fermented foxtail millet starches exhibited an A-type crystal structure. Compared with native samples, the fermented samples performed enhanced proportion of short-branched chain, crystallinity, and short-range ordered degree. After fermentation for 24 h, the solubility, adsorption capacity, and pasting viscosity of foxtail millet starches improved, whereas the swelling power, pasting temperature, breakdown, setback, and degree of retrogradation reduced. Additionally, fermentation increased the transition temperatures, enthalpy, and digestibility. Overall, Lactobacillus plantarum fermentation is considered a competent choice to regulate the characteristics of foxtail millet starch.

Effect of Lactobacillus plantarum and flavourzyme on protein degradation and flavor development in grass carp during fermentation

This study examined the effect of Flavourzyme and Lactobacillus plantarum (L. plantarum) on protein degradation and flavor development during grass carp fermentation. The control groups comprised natural fermentation and fermentation with L. plantarum. Compared with the two control samples, those exposed to combined Flavourzyme and L. plantarum fermentation exhibited lower moisture content and enhanced protein hydrolysis, which accelerated the production of water-soluble taste substances (trichloroacetic acid-soluble peptides and free amino acids). The electronic tongue and electronic nose results indicated that the grass carp subjected to combined fermentation way displayed a more intense umami taste and aroma. Moreover, the sensory evaluation results confirmed that the combined fermentation method significantly improved the taste and odor attributes of fermented grass carp. In conclusion, combined fermentation with Flavourzyme and L. plantarum may effectively reduce fermentation time and enhance the flavor of fermented grass carp products.

Fabrication of Ti3C2Tx/ZnONPs composite with high antibacterial and antibiofilm activity

Microbial contamination poses a serious threat to human health and socioeconomics, and is a major problem for global public health. Herein, we fabricated Ti3C2Tx/ZnONPs composite by using Lactobacillus plantarum fermentation broth to reduce ZnONPs in situ on few-layer Ti3C2Tx MXene after etching and delamination treatment. Antibacterial experiments showed that the Ti3C2Tx/ZnONPs composite exhibited significant antibacterial and antibiofilm activity against both Gram-negative E. coli and Gram-positive S. aureus. Moreover, the exploration of the antibacterial mechanisms demonstrated that Ti3C2Tx/ZnONPs could inhibit and kill bacteria by disrupting bacterial cell wall/membrane, causing leakage of intracellular contents, interfering with metabolism and inducing oxidative stress. The synergistic effect of multiple antibacterial mechanisms can effectively prevent the evolution of resistance. Overall, as a novel inorganic antibacterial material, Ti3C2Tx/ZnONPs composite holds a promising application in the antimicrobial field.

Fabrication of polyvinyl alcohol/vanillin/Ti3C2Tx/ZnONPs composite film with excellent antimicrobial properties for pepper preservation

Novel food packaging materials with antimicrobial properties must be developed to ensure that fresh agricultural products are free from microbial contamination during the process from “farm” to “table”. Herein, we synthesized an antimicrobial composite packaging film by employing a green in situ synthesis method. The method involves the in situ reduction of zinc oxide nanoparticles (ZnONPs) on the substrate Ti3C2Tx by Lactobacillus plantarum fermentation broth, which was then blended with polyvinyl alcohol and vanillin to obtain the polyvinyl alcohol/vanillin/Ti3C2Tx/ZnONPs (PVA/VAN/T-Z) composite film. The incorporation of crosslinker VAN and antimicrobial material Ti3C2Tx/ZnONPs did not affect the transparency and color of the film, but improved its mechanical strength, hydrophobicity, and antimicrobial ability of the film. Antimicrobial experiments demonstrated that the PVA/VAN/T-Z composite film exhibited significant antimicrobial activity against bacteria (Gram-negative E. coli and Gram-positive S. aureus) and fungi isolated from peppers. Furthermore, pepper preservation experiments demonstrated that the PVA/VAN/T-Z composite film exhibited commendable antimicrobial and preservation performance compared to commercially available film. As a novel antimicrobial packaging material, the multifunctional PVA/VAN/T-Z composite film has a broad application prospect in food preservation.

Widely targeted metabolomics-based analysis of the impact of L. plantarum and L. paracasei fermentation on rosa roxburghii Tratt juice

Rosa roxburghii Tratt fruits (RRT) exhibit extremely high nutritional and medicinal properties due to its unique phytochemical composition. Probiotic fermentation is a common method of processing fruits. Variations in the non-volatile metabolites and bioactivities of RRT juice caused by different lactobacilli are not well understood. Therefore, we aimed to profile the non-volatile components and investigate the impact of L. plantarum fermentation (LP) and L. paracasei fermentation (LC) on RRT juice (the control, CG). There were both similarities and differences in the effects of LP and LC on RRT juice. Both of the two strains significantly increased the content of total phenolic, total flavonoid, and some bioactive compounds such as 2-hydroxyisocaproic acid, hydroxytyrosol and indole-3-lactic acid in RRT juice. Interestingly, compared with L. paracasei, L. plantarum showed better ability to increase the content of total phenolic and these valuable compounds, as well as certain bioactivities. The antioxidant capacity and α-glucosidase inhibitory activity of RRT juice were notably enhanced after the fermentations, whereas its cholesterol esterase inhibitory activity was reduced significantly. Moreover, a total of 1466 metabolites were identified in the unfermented and fermented RRT juices. There were 278, 251 and 134 differential metabolites in LP vs CG, LC vs CG, LC vs LP, respectively, most of which were upregulated. The key differential metabolites were classified into amino acids and their derivatives, organic acids, nucleotides and their analogues, phenolic acids and alkaloids, which can serve as potential markers for authentication and discrimination between the unfermented and lactobacilli fermented RRT juice samples. The KEGG enrichment analysis uncovered that metabolic pathways, purine metabolism, nucleotide metabolism and ABC transporters contributed mainly to the formation of unique composition of fermented RRT juice. These results provide good coverage of the metabolome of RRT juice in both unfermented and fermented forms and also provide a reference for future research on the processing of RRT or other fruits.

Biotransformation of bitter gourd (Momordica charantia) by Lactobacillus plantarum and its bioactivities

Bitter gourd is renowned for its various bioactivities, including antioxidant, antiglycation, and antiplatelet aggregation. However, the bioactivity and bioavailability of plant extracts could be low. Biotransformation through Lactobacillus plantarum fermentation is capable of enhancing these beneficial properties. Therefore, the present work aimed to investigate the physical and pH profiles, total phytochemical contents, bioactive contents, and bioactivities of the juices of unfermented bitter gourd (UBG) and fermented bitter gourd at 48 (FBG-48) and 96 (FBG-96) h. Fermentation gradually altered the physical and pH profile of bitter gourd, while non-significant decrease was seen in the total flavonoid content (p &gt; 0.05). The highest total phenolic content was observed in FBG-48, followed by UBG and FBG-96. UBG exhibited the highest total triterpenoid content, followed by FBG-48 and FBG-96. Interestingly, fermentation increased the antioxidant, antiglycation, and anti-aggregation activities of bitter gourd. FBG-48 demonstrated the highest antioxidant and antiglycation activities, with 10.77 and 8.68% higher activity, respectively, compared to UBG and FBG-96. Meanwhile, FBG-96 exhibited the highest antiglycation activity, with 60% increase. These could have been attributed to the biotransformation of tannic acid into syringic acid, and momordicoside Q into kuguacin P, along with the potential release of p-coumaric acid and caffeic acid from the cell walls. These findings demonstrated bitter gourd’s promising role in type-II diabetes complication treatment, particularly through its protein aggregation inhibition activity, and that fermentation could increase its bioactivities.

Studies on the Changes of Fermentation Metabolites and the Protective Effect of Fermented Edible Grass on Stress Injury Induced by Acetaminophen in HepG2 Cells

In this study, gas chromatography-mass spectrometry (GC-MS) based untargeted metabolomics was used to describe the changes of metabolites in edible grass with Lactobacillus plantarum (Lp) fermentation durations of 0 and 7 days, and subsequently to investigate the protective effect of fermented edible grass on acetaminophen-induced stress injury in HepG2 cells. Results showed that 53 differential metabolites were identified, including 31 significantly increased and 22 significantly decreased metabolites in fermented edible grass. Fermented edible grass protected HepG2 cells against acetaminophen-induced stress injury, which profited from the reduction in lactate dehydrogenase (LDH) and malondialdehyde (MDA) levels and the enhancement in superoxide dismutase (SOD) activity. Cell metabolomics analysis revealed that a total of 13 intracellular and 20 extracellular differential metabolites were detected. Fermented edible grass could regulate multiple cell metabolic pathways to exhibit protective effects on HepG2 cells. These findings provided theoretical guidance for the formation and regulation of bioactive metabolites in fermented edible grass and preliminarily confirmed the protective effects of fermented edible grass on drug-induced liver damage.

Intensification of rice flour gel structure by fermenting corresponding rice with Lactobacillus plantarum

In starch gel foods processing, lactic acid fermentation is an effective strategy to improve the quality of the gel. This study revealed the effects of Lactobacillus plantarum fermentation for rice on the textural and rheological properties of the corresponding gels. The hardness, adhesiveness and chewiness of the gel showed ascending trends with the forwarding of fermentation. The role of Lactobacillus plantarum on rheological properties of gel depended on fermentation time. As the time was within 3 days, the process reduced the viscoelastic of the gel, while as the time was for 5 days, the process enhanced the viscoelastic of the gel. During fermentation, amylose content increased from 21.56 ± 1.17% to 27.39 ± 0.63%, and crude protein content descended from 12.60 ± 0.44 g/100 g DW to 4.8 ± 0.49 g/100 g DW. Total organic acids were ascending in the whole process, and lactic acid (LA), acetic acid (AA) and citric acid (CA) made the dominant contribution. The enthalpy change (ΔH) of the rice flour fermented for 5 days was significantly (p < 0.05) increased to 9.90 ± 0.24 J/g, indicating the formation of more double helix structures. These organic acids may contribute to the formation of the pores on the surface of granules by hydrolyzing the components, which provides a channel for enzymes to enter the interior of granules. These results provide the basis for the development of fermented rice-based foods.

High-throughput screening for aroma production in food fermentations

A microtiter plate (MTP) method was developed to screen 1064 unique microorganisms-substrate fermentations for production of 68 target aroma compounds. Based on the number of hits identified by GC–MS, 50 fermentations were repeated at 50-mL scale in flasks. Comparison of GC–MS data showed that scaling up from MTP to flask did not generally result in large differences between the volatile profiles, even with a wide variety of substrates (juice, food slurry and food side-streams) and microorganisms (yeast, bacteria and fungi) used. From the screening results, Lactobacillus plantarum fermentation of chilli pepper was further studied as a high amount of phenols, especially guaiacol and 4-ethylphenol, was produced after fermentation. From HPLC-MS and sensory analysis, capsaicin was shown to be a probable precursor for these phenols and a potential mechanism was proposed. The protocol described herein to screen aroma compounds from fermentation of agri-food products and side streams can support development of clean label flavourful food ingredients.

Effect of Lactiplantibacillus plantarum fermentation on the physicochemical, antioxidant activity and immunomodulatory ability of polysaccharides from Lvjian okra

Okra polysaccharides exhibits a range of biological activities. To date, its processing using microbial fermentation has not been explored. This study investigated the fermentation of okra juice with various lactic acid bacteria, followed by the extraction and characterization of crude polysaccharides (termed OPS-F), in contrast to their non-fermented counterpart (OPS). Changes in physicochemical properties, antioxidant activity and immunomodulatory ability were noted. The results demonstrated that OPS-F had a 7.42–12.53 % increase in total polysaccharides content compared to OPS. However, high-performance size-exclusion chromatography indicated a reduction in the molecular weight of OPS-F (7.9–9.5 × 105 Da) relative to OPS (1.66 × 106 Da). Compared to OPS, OPS-F had reduced levels of mannose, glucose, glucuronic acid and arabinose, but increased rhamnose, galacturonic acid and galactose, exhibiting enhanced solubility and lower apparent viscosity. Fourier transform infrared spectroscopy and nuclear magnetic resonance analysis showed minimal changes in polysaccharide structure post-fermentation. Moreover, despite a decrease in antioxidant activity post-fermentation, OPS-F exhibited superior immunomodulatory potential. In conclusion, fermenting okra juice with lactic acid bacteria alters the physicochemical properties of crude polysaccharides and enhances their immunomodulatory activity, offering a promising approach for developing new functional food resources.

Effects of tandem fermentation of edible mushroom and L. plantarum on sensory, polysaccharide, vitamin C, and γ-aminobutyric acid of Rosa roxburghii Tratt and coix seed beverage

A new Rosa roxburghii Tratt (RRT) and coix seed (CS) beverage rich in multi-active ingredients was developed. Edible mushrooms and L. plantarum were selected for fermentation in stages. Some physicochemical properties, γ-aminobutyric acid (GABA), polysaccharides and sensory were studied during the T. versicolor and L. plantarum fermentation. T. versicolor increased the free amino acid through enzymatic protein digestion in the early growth stage and used these amino acids to synthesize its bacteriophage protein. T. versicolor and L. plantarum increased the polysaccharide and GABA of the fermentation broth. Vitamin C was retained as much as possible, with a slight loss occurring mainly in the aerobic fermentation stage of T. versicolor. Its less loss in exchange was for a higher value of T. versicolor polysaccharide, protein enhancement, and bitterness reduction. This study provides a reference for the deep processing of Guizhou's unique agricultural products and edible mushroom fermented beverage.

Lactiplantibacillus plantarum fermentation enhanced the protective effect of kiwifruit on intestinal injury in rats: Based on mitochondrial morphology and function

Fermented foods have protective effects on body health. In our previously study, we found Lactiplantibacillus plantarum fermentation enhanced antioxidant activity of kiwifruit in vitro digestion. Then, in this work we explored the protective effect of fermented kiwi on intestinal injury induced by acute lipopolysaccharide (LPS) stress. Compared to non-fermented kiwi pulp (KP), Lactiplantibacillus plantarum fermented kiwi pulp (FKP-LP) contained more peptides, hormones and vitamins contents, lesser nucleic acid and carbohydrate contents. FKP-LP could relieve the intestinal injury by improving morphological of tight junction and upregulating tight junction proteins mRNA expression. Fermented kiwi maintained the mitochondrial morphology, mitochondrial respiratory function, and mitochondrial homeostasis, and relieved the LPS induced injury by regulating the contents of energy substances, and the respiratory chain complex enzyme activity through the pathway of AMPK and its downstream factors including PGC-1α, NRF1, NRF2, TFAM, and ULK2.

Klebsiella as an α-tocopherol source facilitating Lactobacillus plantarum fermentation in rice straw silage1

Silage serves as the indispensable diet of ruminants, the increasing mechanism of α-tocopherol during silage making is unclear. Rice straw lacks chlorophyll after harvesting the grain, this can eliminate the impact of tocopherols formed by the breakdown of chlorophyll. Here, we explored the α-tocopherol source, its influencing factor, and its relationship with dominant lactic acid bacteria in rice straw silage treated without or with different additives (sodium benzoate, Lactobacillus plantarum, cell wall degrading enzymes, the combination of Lactobacillus plantarum and cell wall degrading enzymes) and vacuum times (5, 8, 11, and 14 s) after ensiling for 42 d. We found that the pathogenic Klebsiella was traced as the source of increased α-tocopherol in rice straw silage. The residue air in the silo, pH value, and additive variety had impacts on Klebsiella activity, which was strongly active at levels of residue air in the silo and pH that were high. As an acidic niche creator, Lactobacillus plantarum was more effective than sodium benzoate in restraining Klebsiella. Despite having a low acidity tolerance, Klebsiella was still present in rice straw silage treated with L. plantarum. The relationship between Klebsiella and L. plantarum was that Klebsiella could afford α-tocopherol to the multiplication of L. plantarum and residue capsular polysaccharide protected Klebsiella from escaping the extinction in rice straw silage.

Changes in physicochemical characteristics and metabolites in the fermentation of goji juice by Lactiplantibacillus plantarum

Untargeted and targeted metabolomics based on LC-MS/MS was applied here to investigate the changes in metabolites following Lactiplantibacillus plantarum (L. plantarum) fermentation of goji juice. The changes in physicochemical characteristics, free amino acid and organic acid levels were quantified. Total phenols, total flavonoids, and antioxidant activity were increased after these L. plantarum fermentation. 31 primary metabolites were screened out by comparison between two groups using multivariate statistical analysis. L. plantarum consumed reducing sugar and most varieties of amino acids. Gamma amino butyric acid (GABA) and phenylacetaldehyde were significantly accumulated via precursor of glutamate and phenylalanine, respectively. Indole-3-lactic acid (ILA) was the characteristic secondary metabolite after fermentation. There were 6.25 and 4.19 mg/L ILA accumulated after LP-D and LP-F fermentation, respectively, whereas it was not detected in goji juice. The accumulation of tyrosol was strain-dependent. Part of the bitter-taste amino acids, including l-methinoine, l-phenylalanine and tryptophan, were converted into their corresponding acetyl-derivatives, which represented umami or kokumi taste. Overall, fermentation by L. plantarum strains altered the metabolite profile and increased the levels of several biologically active substances of goji juice. These results deepen the understanding of L. plantarum metabolism, and the bioconversion associated with flavor and bioactive compounds unraveled here can be used as references in other plant-based materials for LAB fermentation.