Liquid-state Fermentation Research Articles

Optimization of Liquid Fermentation of Acanthopanax senticosus Leaves and Its Non-Targeted Metabolomics Analysis

To enhance the nutritional value of Acanthopanax senticosus leaves (AL), a fermentation process was conducted using a probiotic Bacillus mixture, and the changes in chemical constituents and biological activities before and after fermentation were compared. A response surface methodology was employed to optimize the liquid fermentation conditions of AL based on their influence on polyphenol content. Non-targeted metabolomics analysis was performed using LC-MS/MS to reveal the differing profiles of compounds before and after fermentation. The results indicated that Bacillus subtilis LK and Bacillus amyloliquefaciens M2 significantly influenced polyphenol content during fermentation. The optimal fermentation conditions were determined to be a fermentation time of 54 h, a temperature of 39.6 °C, and an inoculum size of 2.5% (v/v). In comparison to unfermented AL, the total polyphenol and flavonoid contents, as well as the free radical scavenging capacities measured by DPPH and ABTS assays, and the activities of β-glucosidase and endo-glucanase, were significantly increased. The non-targeted metabolomics analysis identified 1348 metabolites, of which 829 were classified as differential metabolites. A correlation analysis between the differential metabolites of polyphenols, flavonoids, and antioxidant activity revealed that 13 differential metabolites were positively correlated with antioxidant activity. Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis of the differential metabolites identified 82 pathways, with two of the top 25 metabolic pathways related to flavonoids. This study explores the potential for enhancing the active ingredients and biological effects of AL through probiotic fermentation using Bacillus strains.

Phenolic Bisabolane Sesquiterpene Derivatives from an Arctic Marine-derived Fungus Aspergillus sydowii MNP-2

Background:: Filamentous fungi in the genus Aspergillus are well known for their important roles in production of bioactive secondary metabolites with diversely chemical structures and potential application in pharmaceutical industry. Objective:: The present study aimed to investigate the phenolic bisabolane sesquiterpene (PBS) derivatives from an Arctic marine-derived fungus Aspergillus sydowii MNP-2. Methods:: In this study, antimicrobial activities were carried out according to the broth microdilution assay, nitric oxide (NO) production in mouse macrophages (RAW264.7) and BV2 microglial cells was used to detect the inhibitory effect of compounds in inflammatory reactions, and in vitro inhibitory cell proliferation activity was determined by the cell counting kit-8 (CCK-8) assay. Results:: In this work, chemical investigation of an Arctic marine-derived strain A. sydowii MNP-2 led to the isolation of 11 PBSs (1-11) using various chromatographic methods. Their chemical structures were unambiguously determined by 1H NMR spectroscopy and mass spectrometry analyses as well as comparison with literature data. It is noteworthy that compounds 1, 7 and 11 were firstly obtained from A. sydowii. Antimicrobial assay showed that these chemicals had no potent inhibitory effect on Staphylococcus aureus, Escherichia coli, and Candida albicans with MIC values > 16 μg/mL. Additionally, the inhibition of nitric oxide (NO) production in lipopolysaccharide (LPS)- induced inflammation in mouse macrophages (RAW264.7) and BV2 microglial cells were all below 10% for compounds 4-6 and 8, indicating almost negligible anti-inflammatory efficacy. Among the tested compounds 4-6 and 8 for tumor-cell proliferation inhibition activities, compound 5 demonstrated the strongest inhibitory effect against human acute promyelocytic leukemia cells (HL-6) with a 44.76% inhibition rate. Conclusion:: In the present study, 11 PBS derivatives were purified and characterized from the solidand liquid-state fermentations of the Arctic marine-derived fungus A. sydowii MNP-2. Unfortunately, none of these metabolites had significant antimicrobial, anti-inflammatory, or tumor-cell proliferation inhibition activities.

Oscillation-static cycle cultivation enhances the synthesis of triterpenes and mycelium activity in Ganoderma lucidum

Ganoderma lucidum is a precious fungus with both edible and medicinal values and has a long history of medical use. Triterpenes as the main active components endow G. lucidum with anti-tumor, antioxidant, and other pharmacological activities. The present study endeavors to establish a proficient liquid-state fermentation technology for the enhanced production of triterpenes. In view of the limitations inherent in conventional submerged fermentation and oscillation-static two-stage cultivation, this study established an oscillation-static cycle cultivation process and optimized the cultivation conditions by building an artificial neural network model based on genetic algorithms. The cultivation conditions for the high-yield production of triterpenes were optimized as follows: 2.8 days of oscillation, 7.3 days of static cultivation, 0.2 day of oscillation, and 0.3 day of static cultivation. Under these conditions, the content of triterpenes reached 20.82 mg/g. The yield of triterpenes reached 129.09 mg/L, showing a remarkable increase of 324.78% compared with that of the Z10J0 method. Moreover, the established method shortened the cultivation cycle by 10.6 days. The mycelia cultivated under this regimen exhibited commendable anti-tumor and antioxidant activities. This study not only presents an economical liquid-state fermentation approach but also streamlines the fermentation flow, reduces fermentation duration, and effectively ameliorates drawbacks associated with conventional cultivation methods. In addition, this study gives valuable insights into the scaled application of liquid-state fermentation in the high-yield production of triterpenes, which showcases broad prospects.

Effects of different fermentation processes on cooking and eating quality of brown rice noodles

While brown rice noodles are nutritionally dense, their subpar cooking and eating attributes render them unpalatable to consumers. Fermentation serves as a viable method to enhance food quality and taste. In our previous study, the quality of brown rice noodles was notably enhanced through solid-state fermentation of rice flour (SFRF) with Limosilactobacillus fermentum. In this study, we investigated the impact of SFRF, solid-state fermentation of rice grains (SFRG), and liquid-state fermentation of rice grains (LFRG) on the cooking attributes, sensory qualities, and processing characteristics of brown rice noodles (BRN). The findings indicated that the quality of brown rice noodles (BRN) could be notably enhanced through the application of these three fermentation techniques. In comparison to the BRN produced via SFRF and LFRG, the rice noodles processed using SFRG exhibited superior visual appeal, reduced cooking losses (4.87%), minimal breakage rates (4.00%), and enhanced taste profile. Following fermentation, the gelatinization temperature (Tp) and peak viscosity of rice flour decreased, with SFRG demonstrating the lowest gelatinization temperature. Pasting and rheological assessments revealed that solid-state fermentation of rice grains led to a reduction in the pasting viscosity of rice flour by hindering starch granule swelling and disintegration. In summary, noodles processed through SFRG exhibited enhanced cooking and sensory characteristics, luminosity (L*), and superior gel structure.

Improving the Quality of Low-grade Tobacco by Enzymatic Treatment and Co-fermentation with Yeast and Lactic Acid Bacteria.

Enzymatic treatment is a promising method to modulate the chemical composition, flavoring substances and to enhance the sensory quality of cigarettes. This study investigates the feasibility of enzymatic treatment in conjunction with co-fermentation with yeast and lactic acid bacteria to improve the quality of low-quality cigarettes. Amylase, flavourzyme, glucoamylase, protease, and their combinations were used for the enzymatic treatment of tobacco-sorghum by using the liquid-state fermentation method. The biochemical components and flavor substances of the fermented products were analyzed. The findings show that amylase and glucoamylase can effectively degrade starch into fermentable reducing sugars, facilitate microbial growth and proliferation, and significantly enhance the levels of flavoring alcohols and esters. Flavourzyme and glucoamylase, either individually or combined with amylase, achieved a more balanced distribution of flavor substances in the products. Additionally, flavourzyme was capable of increasing the content of guaiacol, solanesol, and 2-acetylpyrrole in the fermented products, thereby improving the richness and depth of the cigarette flavor. While the protease treatment group showed fewer flavor substances and higher nicotine content, which was detrimental to the quality of cigarettes. When integrating the fermentation products into low-quality cigarettes, flavourzyme and glucoamylase combined with amylase treatment received higher scores in sensory quality evaluations. This study provides a beneficial strategy for effectively improving the quality of low-quality cigarettes.

Determinant factors for optimal anaerobic digestion of agro-industrial sardine residues

ABSTRACT In this study, nutritious and abundant waste generated by sardine canneries was used as the main substrate to assess the effect of fundamental parameters in anaerobic digestion. The temperature range studied, between 37°C and 45°C, allowed for a comparison between the performance of the thermophilic and mesophilic processes. The free water content in the substrate also enabled us to compare fermentation in solid-state fermentation (SSF) with its counterpart, liquid-state fermentation (LSF). The study parameters also included the integration of Aspergillus niger (AN) and molasses. The results revealed significant effects of the AN inoculum and thermophilic conditions in improving biogas production. Optimal biotransformation generated a safe digestate that complies with French standards for use as a biofertilizer. Germination tests demonstrated that it has no inhibitory effect on tomato seeds and has the potential to enhance crop yields better than chemical fertilisers.

Effect of linolenic acid on triterpenoids production by the liquid fermentation of Antrodia cinnamomea.

Liquid state fermentation is now a commonly used route to obtain triterpenoids from Antrodia cinnamomea, and linolenic acid can significantly promote triterpenoids synthesis, whereas its action mechanism has not been studied. Here, we comprehensively performed an investigation on the mechanism of linolenic acid to promote triterpenoids production in liquid-state fermentation of A. cinnamomea. Results showed that the addition of linolenic acid increased the unsaturated fatty acid index, fluidity, and permeability in the cell membrane of A. cinnamomea mycelia, favored the absorption of nutrients in the medium by the mycelium, enhanced the material exchange inside and outside, and thus promoted mycelial growth and triterpenoids synthesis. Moreover, 767 significantly differentially expressed genes were detected by adding linolenic acid, including 212 upregulated genes and 555 downregulated genes. The upregulated genes were mainly enriched in metabolism, glycolytic pathway, TCA cycle, and pyruvate metabolism. It was seen that the addition of linolenic acid improved the cell metabolic activity and promoted the synthesis of secondary metabolites, proving that the addition of linolenic acid improved the metabolic viability of cells and promoted secondary metabolite synthesis.

Fermentation of soybean residue by A. auricula: Mechanisms and uses

The biochemical conversion mechanism of soybean residue by liquid-state fermentation with Auricularia auricula mycelium (AAM) was elucidated through the determination of enzymes and basic nutrients during fermentation as well as the metabolites analysis. The metabolomics analysis was conducted on the differential metabolites of A. auricula using LC-MS/MS and found a total of 351 differential metabolites, including organic acids, sugars, amino acids, phenols etc.; most of which were organic acids, and glycosides. All the differentially expressed compounds were analyzed by KEGG metabolic pathway enrichment. There were 30 metabolic pathways related to the metabolic mechanism of soybean residue conversion; among them, fatty acid synthesis, sugar metabolism, carbon synthesis, and the synthesis of various secondary metabolites were the main metabolic pathways. During the whole fermentation process, the content of flavonoids decreased gradually and its content was 0.001 mg/g after 15 days of fermentation. This indicated that AAM successfully fermented and transformed the soybean dregs into nutritionally rich products. As it was rich in high protein, 3D printing technology was utilized to develop a AAM protein-based cream substitute. The ink exhibited excellent 3D printability owing to its solid viscoelastic behavior. The ink rheology was controlled by XG concentrations, and 3D printed AAM protein emulsion with 2.0% XG showed printing stability. We also produced AAM protein-rich food products using traditional culinary processing techniques. It provided a theoretical basis for realizing the comprehensive utilization of soybean residue and can be used as a new protein source in the food industry with good application prospects.

Plicatin C: A New Cinnamate Derivative from Mangrove-derived Fungus Aspergillus terreus DM62

Background: Marine fungi have been proven to be a new arsenal for the discovery of valuable secondary metabolites. Method:: Fungus strain Aspergillus terreus DM62 was initially fermentated using solid corn medium and PDA liquid medium. Subsequently, extensive chromatographic methods were applied to isolate the fermentation cultures of DM62, and the chemical structures of isolate compounds were elucidated by pectroscopic analyses and optical rotations comparison. Additionally, α-glucosidase and ATPcitrate lyase (ACL) inhibitory activities of isolate compounds were assessed to investigate their hypoglycemic and lipid-lowering activities. Result:: A new cinnamate derivative, plicati n C (1), together with 18 known compounds, were isolated from the solid and liquid state fermentations of A. terreus DM62. Activity evaluation showed that compounds 3, 6, and 8-10 exhibited stronger α-glucosidase inhibitory activities than acarbose at 400 μM, and butenolide 3, with an IC50 value of 21.5 μM, was discovered with significant ACL inhibitory activity for the first time. Conclusion:: This study not only discovered a new cinnamate derivative but also found butenolides with potent ACL inhibitory activity, which is favorable to clarify their pharmacological mechanism in the treatment of metabolic disease.

Dynamics changes in metabolites and pancreatic lipase inhibitory ability of instant dark tea during liquid-state fermentation by Aspergillus niger

Instant dark tea (IDT), prepared by liquid-state fermentation using Aspergillus niger, is known for its high theabrownins content and lipid-lowering effect. To explore the impact of fungal fermentation on IDT compositions and its pancreatic lipase inhibitory ability (PLIA), untargeted and targeted metabolomic analysis were applied to track the changes of metabolites over a 9-day fermentation period, and correlation analysis was then conducted between metabolites and PLIA of IDT. There were 54 differential metabolites exhibited significant changes from day 3 to day 5 of fermentation. The concentrations of theabrownins and caffeine increased during fermentation, while phenols and free amino acids decreased. The PLIA of IDT samples significantly increased from day 5 to day 9 of fermentation. Theabrownins not only positively correlated with the PLIA but also exhibited a high inhibition rate. These findings provide a theoretical basis to optimize the production of IDT as functional food ingredient.

Enzyme production by the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae and their application in the control of nematodes (Haemonchus spp. and Meloidogyne incognita) in vitro

Brazil is affected by the infection of gastrointestinal nematodes (Haemonchus spp.) because it causes subclinical diseases in small ruminants that directly affect weight and milk production and, in turn, generate a health risk for the animals. In the same way root-knot nematodes (Meloidogyne incognita) is a serious disease, which parasitize the roots of tomato plants causing damage such as poor nutrient absorption leading to significant yield losses. In order to minimize the economic impact of these nematodes, it is important to establish new control strategies. Beauveria bassiana and Metarhizium anisopliae are two main mycoinsecticides used to control many orders of insects, such as Lepidoptera and Hemiptera. These fungi have the ability to produce extracellular enzymes, which play an important role to control in the pest infection process. The aim of this study was to evaluate the production of proteases and chitinases by the entomopathogenic fungi B. bassiana and M. anisopliae on different solid and liquid culture media and their application in vitro to the control of Haemonchus spp and Meloidogyne incognita. To achieve this goal, enzymes were produced under solid and liquid fermentation conditions to determine the highest chitinolytic and proteolytic activity of commercial two strain of B. bassiana (IBCB 66 and ESALQ PL63) and M. anisopliae (IBCB 425 and ESALQ E9) in liquid media: SDY broth, YPG culture medium, synthetic, and soluble starch with yeast extract. The solid media tested were: rice supplemented with whey and chrysalis flour mixed with rice. In addition, the nematicidal action of their extracts (containing concentrated enzymes and without fungal cells) was measured. The results showed that the best culture medium (p< 0.01) for protease was solid serum rice medium, with a value for M. anisopliae IBCB 425 of 52 U/mg, and for B. bassiana ESALQ PL63 the value was 36 U/mg, compared to all the tested media. On the other hand, for chitinase of M. anisopliae strain IBCB 425, the activity value was close to 0.60 U/mg. In contrast, for B. bassiana isolate ESALQ PL63, SDY medium was the best inducer for chitinase production, with a value of 0.90 U/mg. Regarding the nematicidal activity of the crude extracts, the reduction percentages were 58% for ESALQ PL63 and 100% for IBCB 425 in the case of animal parasites. For plant parasites, the reduction percentages were 19% for ESALQ PL63 and 71% for IBCB 425. Thus, the use of enzyme-rich crude extracts presents promising control options for pest control.

A Method of Reducing Salt Content in Fermented Soy Sauce Improves Its Flavor and Quality.

Most commercially available soy sauce is fermented by high-salt liquid-state (HS) fermentation, which has an excessive salt content and a long fermentation period. In this study, a new salt-reduced fermentation (SR) soy sauce technology involving multiple strains of bacteria was developed to reduce consumers' salt intake. The SR soy sauce was found to have an amino acid nitrogen content of 8.40 g/L and over 80 kinds of flavor substances, which were significantly higher than those of low-salt solid-state fermented soy sauce and approximately equal to HS soy sauce. Compared with HS soy sauce, the salt content of the SR soy sauce was reduced by 59.2%, achieving the salt reduction goal. The proportion of umami amino acids in SR soy sauce reached 32.0% of the total level, enhancing SR soy sauce's quality. Hence, the new fermentation process can decrease salt content and shorten fermentation time.

Optimization of Stationary Liquid Fermentation Conditions for N-Methylsansalvamide Production by the Endophytic Strain Fusarium sp. R1

To improve the yield of the therapeutic agent N-methylsansalvamide (SA), optimization of stationary liquid fermentation conditions was conducted on an endophytic strain, Fusarium sp. R1, at flask level. Using a One-Factor-At-a-Time approach, the fermentation conditions for SA production were determined as follows: fermentation time of 13 d, 24 °C, initial pH of 6.5, seed age of 24 h, inoculum size of 5.0% (v/v), loading volume of 50% (v/v), and 20.0 g/L salinity. Sucrose, tryptone, and yeast extract were found to be the best sources of carbon and nitrogen. Using response surface methodology, the optimal medium compositions consisted of 22.5 g/L sucrose, 16.5 g/L tryptone, and 0.024 g/L yeast extract. Verification tests suggested that the SA yield under these optimal conditions reached up to 536.77 ± 2.67 mg/L, which was increased by almost ten times the initial yield (54.05 ± 3.45 mg/L). The findings indicate that a high SA production yield can be achieved by stationary culture of strain R1 under proper fermentation conditions using a low-cost medium. This study paves the way toward industrial-scale SA production by strain R1 for new drug development.

Liquid-State Fermented Ganoderma lucidum GANO99 Regulates Gut Microbiota and Concomitantly Modulates the Behavioral Deficits and Neurohistopathological Hallmarks of Alzheimer’s Disease in a Preclinical Transgenic Mouse Model of Alzheimer’s Disease

Amyloid beta (Aβ) is a neuropathological hallmark of Alzheimer’s disease (AD). Oxidative stress promotes intracellular accumulation of Aβ in patients with AD. The effects of liquid-state fermentation products of Ganoderma lucidum without mycelia on AD improvement or prevention have not been reported. Therefore, this study aimed to determine whether the liquid-state fermented products of G. lucidum GANO99 can alter AD pathology in the brains of APPNL-G-F/NL-G-F model mice. Our results suggest that these products promote the expression of superoxide dismutase and inhibit the expression of Aβ and glial fibrillary acidic protein, thereby affecting behavioral, learning, and memory disorders in AD mice. In contrast, G. lucidum GANO99 may regulate the gut microbiota to improve AD pathology. Furthermore, these liquid-state fermented products increased the abundance of intestinal probiotics Bifidobacterium in AD mice. Clinical evidence suggests that these lactic acid bacteria can alleviate AD. Overall, the liquid-state fermented products of G. lucidum GANO99 can act as symbionts by reducing the fermentative role of intestinal microbes and chemo-heterotrophy in AD mice.

Waste Tea-Derived Theabrownins for Solar-Driven Steam Generation.

Solar-driven seawater desalination has been considered an effective and sustainable solution to mitigate the global freshwater crisis. However, the substantial cost associated with photothermal materials for evaporator fabrication still hinders large-scale manufacturing for practical applications. Herein, we successfully obtained high yields of theabrownins (TB), which were oxidation polymerization products of polyphenols from waste and inferior tea leaves using a liquid-state fermentation strategy. Subsequently, a series of photothermal complexes were prepared based on the metal-phenolic networks assembled from TB and metal ions (Fe(III), Cu(II), Ni(II), and Zn(II)). Also, the screened TB@Fe(III) complexes were directly coated on a hydrophilic poly(vinylidene fluoride) (PVDF) membrane to construct the solar evaporation device (TB@Fe(III)@PVDF), which not only demonstrated superior light absorption property and notable hydrophilicity but also achieved a high water evaporation rate of 1.59 kg m-2 h-1 and a steam generation efficiency of 90% under 1 sun irradiation. More importantly, its long-term stability and exceptionally low production cost enabled an important step toward the possibility of large-scale practical applications. We believe that this study holds the potential to pave the way for the development of sustainable and cost-effective photothermal materials, offering new avenues for utilization of agriculture resource waste and solar-driven water remediation.

Solid state fermentation characteristic of rice straw using herbivore s cecum microbes

This study was aimed at identifying highly capable lignolytic microbes from nature for use in Solid State Fermentation (SSF) of rice straw. The SSF silage was prepared in laboratory scale, as the following treatments: uninoculated (control), Lactobacillus plantarum FCC 123 (LP), fiber-degrading fungi (Aspergillus sp.) from horse cecum (FF), and fiber-degrading bacteria (Enterococcus casseliflavus) from buffalo cecum (FB). Incubation was carried out for a month at room temperature. The observed parameters were: organic acids, water-soluble carbohydrate (WSC), microorganism and nutrient composition. Rice straw SSF that was inoculated with LP showed the highest quality of fermentation, indicated by significant highest lactic acid bacteria (LAB) population, and has the lowest of poor bacteria indicators (coliform, aerobic bacteria, and bacilli). The LP treatment also has the highest LAB content and lowest WSC. Among treatments, FB treatment seems to have given a similar result with LP followed by FF. While the chemical composition seems unaffected by treatments. Compared with the fresh material, all fermentation with and without inoculants has reduced neutral detergent fiber (NDF) and increased acid detergent fiber (ADF), but there were no differences among all treatments. Inoculation of both LP and FB could improve rice straw SSF silage quality, but this system could not improve fiber degradation as well as in liquid state fermentation (LSF). Keywords: Microorganism, Organic acid, Silage, Straw, Water soluble carbohydrate

Evaluation of the Mineral, Amino Acid and Antimicrobial Properties of Raw and Fermented Trametes elegans

Mushrooms are known to be sources of food and bioactive compounds with medicinal properties. In this study, the mineral, proximate, amino acid and antimicrobial properties of a wild macrofungus, Trametes elegans was investigated. Standard methods were used to evaluate the mineral, proximate and amino acid content of raw and fermented T.elegans. By soaking in methanol and acetone, extracts from the macrofungus’s powdered fruiting bodies were obtained. Using common microbiological methods, the macrofungus extracts’ antimicrobial activity was assessed on test isolates. In addition, isolation and identification of microorganisms associated with raw and fermented T. elegans was done using standard microbiological techniques. The physicochemical parameters (Temperature, pH and Total Titratable Acid) were also monitored during solid and liquid state fermentation of Trametes elegans. The concentration of carbohydrate (70.24±0.33) was higher in the raw sample, while moisture (3.22±0.13), fat (1.85±0.04) and protein contents (22.48±0.09) were higher in sample subjected to solid fermentation. Also, crude fibre (6.68±0.76) and Ash (3.60±1.39) were higher in sample subjected to liquid fermentation. The micro elements analysed are zinc and iron and macro elements are potassium, magnesium and phosphorus and their values increased in fermented Trametes elegans. Analyses of both essential and non-essential amino acids were conducted. The most common amino acids found in all of the samples examined were glutamic acid, leucine, arginine, and aspartic acid. Cysteine and methionine are the least abundant. The amino acid scores were determined by ratio of the milligrams of amino acid per gram of test protein to the milligrams of amino acid per gram in the reference pattern. The results showed that methionine had the lowest score in the raw sample (3.14) and tryptophan had the highest score (18.17) in T. elegans that had undergone solid fermentation. Methanol and acetone extracts inhibited all test isolates except Lactobacillus plantarum. The commercial drug exhibited higher antibacterial activity compared to the extracts, with a significant difference (P≤ 0.05). The inhibitory zones ranged from 5.50 mm against Bacillus subtilis to 18.13 mm against E. coli. The range of the minimum bactericidal concentration (MBC) was 12.5 to 50 mg/mL, while the minimum inhibitory concentration (MIC) was 12.5 to 50 mg/mL. In light of this findings, T. elegans, could be considered as potential sources of natural antimicrobial and can also be relevant for use as food supplements in animals and man.

Optimization of liquid fermentation conditions for Coprinus comatus to enhance antioxidant activity

Coprinus comatus is an edible and medicinal fungus. In this study, the antioxidant activity of the fermentation product of C. comatus was investigated through optimization of fermentation process. The results indicated that the fermentation product of C. comatus had obvious scavenging ability for 2,2’-Azino-bis(3-ethylbenzothiazoline)-6-sulphonic acid (ABTS) free radical. The EC50 of the n-butanol extract from the fermentation product on ABTS·+ was 0.65 ± 0.02 mg/mL. On this basis, the liquid fermentation conditions of C. comatus were optimized through single factor and response surface optimization experiments according to the scavenging ability of ABTS·+ to improve the antioxidant capacity of the fermentation product. The results showed that when the 14% of C. comatus was fermented in a culture medium with a C/N ratio of 48:1 for 6 days, the ABTS·+ scavenging ability was the strongest, and the EC50 of n-butanol extract was 0.57 ± 0.01 mg/mL, which was 12.31% higher than the initial activity. This study laid the foundation for the development of C. comatus.

Enzymatic Activity and Amino Acids Production of Predominant Fungi from Traditional Meju during Soybean Fermentation.

To investigate the effect of the predominant fungal species from Korean traditional meju and doenjang on soybean fermentation, the enzymatic activity and amino acid production of twenty-two fungal strains were assessed through solid- and liquid-state soybean fermentation. Enzymatic activity analyses of solid-state fermented soybeans revealed different enzyme activities involving protease, leucine aminopeptidase (LAP), carboxypeptidase (CaP), glutaminase, γ-glutamyl transferase (GGT), and amylase, depending on the fungal species. These enzymatic activities significantly affected the amino acid profile throughout liquid-state fermentation. Strains belonging to Mucoromycota, including Lichtheimia, Mucor, Rhizomucor, and Rhizopus, produced smaller amounts of total amino acids and umami-producing amino acids, such as glutamic acid and aspartic acid, than strains belonging to Aspergillus subgenus circumdati. The genera Penicillium and Scopulariopsis produced large amounts of total amino acids and glutamic acid, suggesting that these genera play an essential role in producing umami and kokumi tastes in fermented soybean products. Strains belonging to Aspergillus subgenus circumdati, including A. oryzae, showed the highest amino acid content, including glutamic acid, suggesting the potential benefits of A. oryzae as a starter for soybean fermentation. This study showed the potential of traditional meju strains as starters for soybean fermentation. However, further analysis of processes such as the production of G-peptide for kokumi taste and volatile compounds for flavor and safety is needed.

Combined volatile compounds and non-targeted metabolomics analysis reveals variation in flavour characteristics, metabolic profiles and bioactivity of mulberry leaves after Monascus purpureus fermentation.

Mulberry leaves (MLs) are widely used in food because of their nutritional and functional characteristics. However, plant cell walls and natural bitterness influence nutrient release and the flavor properties of MLs. Liquid-state fermentation using Monascus purpureus (LFMP) is a common processing method used to improve food properties. The present study used headspace solid-phase micro extraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and non-targeted metabolomics to examine changes in volatile and non-volatile metabolites in MLs. The transformation mechanism of LFMP was investigated by microscopic observation and dynamic analysis of enzyme activity, and changes in the biological activity of MLs were analyzed. LFMP significantly increased total phenolics, total flavonoids, free amino acids and soluble sugars in MLs, at the same time as decreasing phytic acid levels. In total, 92 volatile organic compounds (VOCs) were identified and quantified. VOCs such as (2R,3R)-(-)-2,3-butanediol, terpineol and eugenol showed some improvement in the flavour characteristics of MLs. By using non-targeted metabolomics, 124 unique metabolites in total were examined. LFMP altered the metabolic profile of MLs, mainly in plant secondary metabolism, lipid metabolism and amino acid metabolism. Microscopic observation and dynamic analysis of enzyme activity indicated that LFMP promoted cell wall degradation and biotransformation of MLs. In addition, LFMP significantly increased the angiotensin I-converting enzyme and α-glucosidase inhibitory activity of MLs. LFMP altered the flavour characteristics, metabolite profile and biological activity of MLs. These findings will provide ideas for the processing of MLs into functional foods. In addition, they also provide useful information for biochemical studies of fermented MLs. © 2023 Society of Chemical Industry.