Tri-frequency simultaneous ultrasound pickling for the acceleration of the NaCl content and quality improvement of pork (longissimus dorsi).

BACKGROUND: The pickling process with NaCl is an essential step for pork preservation. This study aimed to investigate the effect of different ultrasonic intensities of tri-frequency simultaneous ultrasound (TSIU) pickling on the NaCl content and quality of pork (longissimus dorsi). After 30 min pickling, the NaCl content, moisture content, pickling yield, cooking loss, textural properties, color, pH, moisture migration and distribution as well as microstructure of pork were assessed. RESULTS: Results showed that among all the ultrasonic treatment intensities (85-150 W L-1), the NaCl content of the sample pickled by an intensity of 101.3 W L-1 was higher than that of other intensities. TSIU 101.3 W L-1 showed 59.95% higher NaCl content than the control sample. In addition, the sample treated with TSIU of 101.3 W L-1 had higher pickling yield and moisture content, better textural properties of pork (including hardness and chewiness), and less cooking loss. The results of the low-field nuclear magnetic resonance showed that, compared with the control group, the relaxation time T21 of the ultrasound-assisted pickling samples increased, while the proportion of T22 (A22) reduction ranged from 175.0% to 379.9%. The microstructure designated that the ultrasonic treatment could facilitate changes in meat texture. CONCLUSION: Ultrasound marination of different intensities promoted the diffusion of NaCl and affected the quality of pork tenderloins. The TSIU at 101.3 W L-1 could better accelerate NaCl transport and homogeneous distribution on meat, thereby improving the sample quality. © 2024 Society of Chemical Industry.

Evolution of volatile compounds of baked dried tofu during catalytic infrared baking process and their correlation with relevant physicochemical properties.

BACKGROUND: Energy-saving and low-carbon baking processes, as well as the need to determine the flavor-forming mechanisms of baked dried tofu, are becoming increasingly necessary. The application of emerging catalytic infrared radiation (CIR) technology in baking of dried tofu is considered of high interest due to the low energy consumption and high baking efficiency compared to traditional baking methods. Hence, this study aimed to investigate the evolution of aroma compounds in baked dried tofu during the CIR baking process and reveal relevant relationships between physical qualities, potential flavor precursors and key volatile compounds. RESULTS: The results showed that the surface color of dried tofu gradually turned an appetizing golden yellow color during the rapid heating process, caused by the uniform infrared radiation from the radiant emitters. Meanwhile, the moisture of dried tofu experienced minimal reduction and the hardness of dried tofu gradually increased with the formation of crust on the surface. In addition, 49 volatile compounds were identified by headspace solid-phase microextraction-gas chromatography-mass spectrometry and 13 substances - 1-hexanol, 1-octen-3-ol, 1-pentanol, heptanal, nonanal, hexanal, (E,E)-2,4-decadienal, (E,Z)-2,4-decadienal, octanal, (E)-2-octenal, (E)-2-nonenal, 2-heptanone and 2-pentylfuran - were confirmed as key aroma compounds. Moreover, the amino acids aspartic acid, glutamic acid, isoleucine, lysine and arginine, and the fatty acids butyric, caprylic, capric, tridecanoic, stearic, oleic and linolenic were responsible for the unique flavor of CIR-baked dried tofu. CONCLUSION: Consequently, the findings can provide a scientific basis for manufacturers to achieve precise quality control and large-scale production of CIR-baked dried tofu products. © 2024 Society of Chemical Industry.

Isolation of a surfactin-producing strain of Bacillus subtilis and evaluation of the probiotic potential and antioxidant activity of surfactin from fermented soybean meal.

BACKGROUND: Surfactin, usually produced by microbial metabolism, has many advantages including low toxicity, high biodegradability, and stability at extreme pH levels and temperatures, making it suitable for industry. However, its commercial production has not yet been achieved. RESULTS: A strain with a strong surfactin-producing ability was isolated and identified as Bacillus subtilis SOPC5, based on the appearance of colonies, microscopic observation, and 16S rDNA sequencing. The isolate exhibited significant tolerance to acid, bile, gastric, and intestinal juices, and was sufficiently susceptible to antibiotics. Bacillus subtilis SOPC5 showed high levels of auto-aggregation and surface hydrophobicity, and a strong capacity to secrete protease, amylase, and cellulase. The strain also exhibited antibacterial activity against Staphylococcus aureus 10 306 with a antibacterial circle diameter of 18.0 ± 1.1 mm. The maximal yield of surfactin (1.32 mg mL-1) was obtained by fermenting soybean meal (SBM) using the isolate under the following conditions: SBM 86 g L-1, inoculation 1.5 × 107 CFU mL-1, FeSO4 1.2 mg L-1, MnSO4 2.6 mg L-1, MgSO4 0.5 mg mL-1, L-Glu 4 mg L-1, temperature 33 °C, duration 120 h, and shaking at 210 rpm. The purity of surfactin was 97.42% as measured by high-performance liquid chromatography (HPLC). The half inhibitory concentration (IC50) values for surfactin to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS·+) were 1.275 ± 0.11 and 0.73 ± 0.08 mg mL-1, respectively. CONCLUSION: This study provides a scientific basis for the application of B. subtilis SOPC5 (as a potential probiotic) and the preparation of its metabolic product (surfactin). © 2024 Society of Chemical Industry.

The process of solid-state fermentation of soybean meal: antimicrobial activity, fermentation heat generation and nitrogen solubility index.

BACKGROUND: Bacillus amyloliquefaciens has excellent protease production ability and holds great prospects for application in the solid-state fermentation of soybean meal (SBM). RESULTS: Among eight strains of bacteria, Bacillus amyloliquefaciens subsp. plantarum CICC 10265, which exhibited higher protease production, was selected as the fermentation strain. The protease activity secreted by this strain reached 106.41 U mL-1 . The microbial community structure differed significantly between natural fermentation and inoculation-enhanced fermented soybean meal (FSBM), with the latter showing greater stability and inhibition of miscellaneous bacterial growth. During fermentation, the temperature inside the soybean meal increased, and the optimal environmental temperature for FSBM was found to be between 35 and 40 °C. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis and nitrogen solubility index (NSI) results demonstrated that solid-state fermentation had a degrading effect on highly denatured proteins in SBM, resulting in an NSI of 67.1%. CONCLUSION: Bacillus amyloliquefaciens subsp. plantarum CICC 10265 can enhance the NSI of SBM in solid-state fermentation and inhibit the growth of miscellaneous bacteria. © 2023 Society of Chemical Industry.

Effect of magnetic field-assisted fermentation on the in vitro protein digestibility and molecular structure of rapeseed meal.

BACKGROUND: There has been a significant growth in demand for plant-derived protein, and this has been accompanied by an increasing need for sustainable animal-feed options. The aim of this study was to investigate the effect of magnetic field-assisted solid fermentation (MSSF) on the in vitro protein digestibility (IVPD) and functional and structural characteristics of rapeseed meal (RSM) with a mutant strain of Bacillus subtilis. RESULTS: Our investigation demonstrated that the MSSF nitrogen release rate reached 86.3% after 96 h of fermentation. The soluble protein and peptide content in magnetic field feremented rapeseed meal reached 29.34 and 34.49 mg mL-1 after simulated gastric digestion, and the content of soluble protein and peptide in MF-FRSM reached 61.81 and 69.85 mg mL-1 after simulated gastrointestinal digestion, which significantly increased (p > 0.05) compared with the fermented rapeseed meal (FRSM). Studies of different microstructures - using scanning electron microscopy (SEM) and atomic force microscopy (AFM) - and protein secondary structures have shown that the decline in intermolecular or intramolecular cross-linking leads to the relative dispersion of proteins and improves the rate of nitrogen release. The smaller number of disulfide bonds and conformational alterations suggests that the IVPD of RSM was improved. CONCLUSIONS: Magnetic field-assisted solid fermentation can be applied to enhance the nutritional and protein digestibility of FRSM. © 2024 Society of Chemical Industry.

Application of fixed-frequency ultrasound in the cultivation of Saccharomyces cerevisiae for rice wine fermentation.

BACKGROUND: Rice wine (RW) fermentation is limited by its long fermentation time, weak taste and unpleasant flavors such as oil and odor. In this study, a novel ultrasound technology of Saccharomyces cerevisiae was used with the aim of improving fermentation efficiency and volatile flavor quality of RW. RESULTS: The results showed that fixed-frequency ultrasonic treatment (28 kHz, 45 W L-1, 20 min) of S. cerevisiae seed culture at its logarithmic metaphase significantly increased the biomass and alcohol yield by 31.58% and 26.45%, respectively, and reduced fermentation time by nearly 2 days. Flavor analysis indicated that the flavor compounds in RW, specifically the esters and alcohols, were also increased in quantity after the ultrasonic treatment of S. cerevisiae seed liquid. Isobutyl acetate, ethyl butyrate, ethyl hexanoate and phenethyl acetate contents were increased by 78.92%, 129.19%, 7.79% and 97.84%, respectively, as compared to the control. CONCLUSION: Ultrasonic treatment of S. cerevisiae reduced fermentation time and enhanced the flavor profile of RW. This study could provide a theoretical and/or technological basis for the research and development of RW. © 2024 Society of Chemical Industry.

Research progress in the application of catalytic infrared technology in fruit and vegetable processing.

Fruit and vegetable processing can effectively maintain the quality and safety of fruit and vegetable-based products while extending the shelf life of products and saving transportation costs. Infrared (IR) technology has been widely used in many operating units of fruit and vegetable processing because of its versatility of uniform heating, high heat transfer efficiency, and minimized damage to fruit and vegetable tissues. Catalytic IR (CIR), compared to traditional electric IR, is powered by natural gas or liquefied gas, which can improve thermal efficiency while significantly saving energy. However, there is no comprehensive overview discussing and summarizing the utilization and application of the CIR technology in fruit and vegetable processing. Therefore, this review aims to highlight recent advances in the application of CIR technology in fruit and vegetable processing. Specifically, a comprehensive discussion of the physicochemical properties and underlying mechanisms of CIR is provided, and its applications as a single method or in combination with other technologies in fruit and vegetable processes, such as blanching, peeling, microbial population reduction, and drying, are also presented. Besides, the currently used laboratory and pilot-scale equipment of CIR has also been summarized.

Production, bioactivities and bioavailability of bioactive peptides derived from walnut origin by-products: a review.

Walnut-origin by-products obtained from walnut oil extraction industry are high in proteins with various physiological functions and pharmacological properties and an extensive potential for usage in producing bioactive peptides. This review presents the current research status of bioactive peptides derived from walnut by-products, including preparation, separation, purification, identification, bioactivities, and bioavailability. A plethora of walnut peptides with multiple biological activities, including antioxidative, antihypertensive, neuroprotective, antidiabetic, anticancer, and antihyperuricemia activities, were obtained from walnut-origin by-products by enzymatic hydrolysis, fermentation, and synthesis. Different bioactive peptides show various structural characteristics and amino acid composition due to their diverse mechanism of action. Furthermore, walnut protein and its hydrolysate present a high bioavailability in human gastrointestinal digestive system. Improving the bioavailability of walnut peptides is needful in the development of walnut industry. However, future research still needs to exploit energy conservation, high efficiency, environmentally friendly and low-cost production method of walnut bioactive peptide. The molecular mechanisms of different bioactive walnut peptides still need to be explored at the cell and gene levels. Additionally, the digestion, absorption, and metabolism processes of walnut peptides are also the focus of future research.

Mangiferin: a review of dietary sources, absorption, metabolism, bioavailability, and safety.

Mangiferin is a potential candidate for use in nutraceutical and functional food applications due to its numerous bioactivities. However, the low bioavailability of mangiferin is a major limitation for establishing efficacy for use. This review describes current information on known food sources and factors that influence mangiferin contents, absorption, and metabolism features, and recent progress that has come from research efforts to increase the bioavailability of mangiferin. We also list patents that targeted to enhance mangiferin bioavailability. Mangifera indica L. is the major dietary source for mangiferin, a xanthone that varies widely in different parts of the plant and is influenced by many factors that involve plant propagation and post-harvest processing. Mangiferin absorption occurs mostly in the small intestine by passive diffusion with varying absorption capacities in different segments of the gastrointestinal tract. Recent research has led to the development of novel technologies to encapsulate mangiferin in nano/microparticle carrier systems as well as generate mangiferin derivatives to improve solubility and bioavailability. Preclinical studies reported that mangiferin < 2000 mg/kg is generally nontoxic. The safety and the increase in bioavailability are key limiting factors for developing successful applications for mangiferin as a nutritional dietary supplement or nutraceutical.Supplemental data for this article is available online at.

Research progress on extraction of active components from apple processing waste.

Apple waste (APW) is the residual product after apple processing, including apple peel, apple core, apple seed, and other components. A large quantity of APW produced is abandoned annually, leading to serious resource waste and environmental pollution. APW is rich in natural active compounds, such as pectin, polyphenols, fatty acids, and dietary fiber, which has a good use value. This paper reviewed the current research on recovering active components from APW. The traditional extraction methods (acid, alkali, physical, enzyme, etc.) and the novel extraction methods (SWE, UAE, MAE, RFAE, etc.) for the recovery of pectin, polyphenols, apple seed oil, apple seed protein, and dietary fiber from APW were systematically summarized. The basic principles, advantages, and disadvantages of different extraction methods were introduced. The requirements of different extraction methods on extraction conditions and the effects of different extraction methods on the yield, quality, and functional activity of extracted products were analyzed. The challenges and future study direction of APW extraction have prospected. This paper aims to provide a reference for other researchers interested in APW extraction, improve the utilization rate of APW and extend the value chain of the apple industry.

Assessment of DNA mutagenicity induced by He-Ne laser using Salmonella typhimurium strains.

Helium-neon (He-Ne) laser mutagenesis is widely used in microbiology and plant breeding. In this study, two frameshift mutant representative strains of Salmonella typhimurium TA97a and TA98 and two base pair substitution types TA100 and TA102 were employed as model microorganisms to assess DNA mutagenicity induced by He-Ne laser (3 J·cm-2·s-1, 632.8 nm) for 10, 20, and 30 min. The results revealed that the optimal laser application was 6 h in the mid-logarithmic growth stage. Low-power He-Ne laser for short treatment inhibited cell growth, and continued treatment stimulated the metabolism. The effects of the laser on TA98 and TA100 were the most prominent. Sequencing results from 1500 TA98 revertants showed that there were 88 insertion and deletion (InDel) types in the hisD3052 gene, of which the InDels unique to laser were 21 more than that of the control. Sequencing results from 760 TA100 revertants indicated that laser treatment created Pro (CCC) in the product of the hisG46 gene more likely to be replaced by His (CAC) or Ser (TCC) than by Leu (CTC). Two unique non-classical base substitutions, CCC → TAC and CCC → CAA, also appeared in the laser group. These findings will provide a theoretical basis for further exploration of laser mutagenesis breeding. KEY POINTS: • Salmonella typhimurium served as model organism for laser mutagenesis study. • Laser promoted the occurrence of InDels in the hisD3052 gene of TA98. • Laser promoted the occurrence of base substitution in the hisG46 gene of TA100.

Characterization of the interaction between allicin and soy protein isolate and functional properties of the adducts.

BACKGROUND: Soybean meal, a by-product of the soybean oil production industry, has a high protein content but the compact globular structure of the protein from soybean meal limits its wide application in food processing. Allicin has been found to have numerous functional properties. In this study, allicin was interacted with soy protein isolate (SPI). The functional properties of the adducts were investigated. RESULTS: Binding with allicin significantly quenched the fluorescence intensity of SPI. Static quenching was the main quenching mechanism. The stability of adducts decreased with increasing temperature. The greatest extent of binding between allicin and sulfhydryl groups (SH) of SPI was obtained at an allicin/SH molar ratio of 1:2. The amino groups of SPI did not bind with allicin covalently. Soy protein isolate was modified by allicin through covalent and non-covalent interactions. Compared with SPI, the emulsifying activity index and foaming capacity of adducts with a ratio of 3:1 were improved by 39.91% and 64.29%, respectively. Soy protein isolate-allicin adducts also exhibited obvious antibacterial effects. The minimum inhibitory concentrations (MICs) of SPI-allicin adducts on Escherichia coli and Staphylococcus aureus were 200 and 160 µg mL-1 , respectively. CONCLUSION: The interaction of allicin with SPI is beneficial for the functional properties of SPI. These adducts can be used in different food formulations as emulsifiers, foamers, and transport carriers. © 2023 Society of Chemical Industry.

Ultrasonic washing as an abiotic elicitor to increase the phenolic content in fruits and vegetables: A review.

Ultrasonic washing has been widely applied to the postharvest storage of fruits and vegetables as a residue-free physical washing technology, which plays an important role in improving shelf-life, safety, and nutritional value. Phenolics are a large group of phytochemicals widespread in fruits and vegetables, and they have been considered potential protective factors against some diseases because of potent antioxidative properties. Previous studies have shown that ultrasonic washing can increase the phenolic content of fruits and vegetables immediately or during storage through the induction of plant stress responses, which is of great significance for improving the functional and nutritional value of fruits and vegetables. However, the mechanisms of ultrasound as an elicitor to improve the phenolic content remain controversial. Therefore, this review summarizes the applications of ultrasonic washing to increase the phenolic content in fruits and vegetables. Meanwhile, the corresponding physiological stress response mechanisms of the phenolic accumulation in terms of immediate stress responses (i.e., higher extractability of phenolics) and late stress responses (i.e., metabolism of phenolics) are expounded. Moreover, a hypothetical model is proposed to explain phenolic biosynthesis triggered by signaling molecules produced under ultrasound stress, including primary signal (i.e., extracellular adenosine triphosphate) and secondary signals (e.g., reactive oxygen species, Ca2+ , NO, jasmonates, and ethylene). Additionally, the techno-economic feasibility of ultrasonic washing technology is also discussed. Further, challenges and trends for further development of ultrasonic washing as an abiotic elicitor applied to the postharvest storage of fruits and vegetables are presented.

Ultrasonic and homogenization: An overview of the preparation of an edible protein-polysaccharide complex emulsion.

Emulsion systems are extensively utilized in the food industry, including dairy products, such as ice cream and salad dressing, as well as meat products, beverages, sauces, and mayonnaise. Meanwhile, diverse advanced technologies have been developed for emulsion preparation. Compared with other techniques, high-intensity ultrasound (HIUS) and high-pressure homogenization (HPH) are two emerging emulsification methods that are cost-effective, green, and environmentally friendly and have gained significant attention. HIUS-induced acoustic cavitation helps in efficiently disrupting the oil droplets, which effectively produces a stable emulsion. HPH-induced shear stress, turbulence, and cavitation lead to droplet disruption, altering protein structure and functional aspects of food. The key distinctions among emulsification devices are covered in this review, as are the mechanisms of the HIUS and HPH emulsification processes. Furthermore, the preparation of emulsions including natural polymers (e.g., proteins-polysaccharides, and their complexes), has also been discussed in this review. Moreover, the review put forward to the future HIUS and HPH emulsification trends and challenges. HIUS and HPH can prepare much emulsifier-stable food emulsions, (e.g., proteins, polysaccharides, and protein-polysaccharide complexes). Appropriate HIUS and HPH treatment can improve emulsions' rheological and emulsifying properties and reduce the emulsions droplets' size. HIUS and HPH are suitable methods for developing protein-polysaccharide forming stable emulsions. Despite the numerous studies conducted on ultrasonic and homogenization-induced emulsifying properties available in recent literature, this review specifically focuses on summarizing the significant progress made in utilizing biopolymer-based protein-polysaccharide complex particles, which can provide valuable insights for designing new, sustainable, clean-label, and improved eco-friendly colloidal systems for food emulsion. PRACTICAL APPLICATION: Utilizing complex particle-stabilized emulsions is a promising approach towards developing safer, healthier, and more sustainable food products that meet legal requirements and industrial standards. Moreover, the is an increasing need of concentrated emulsions stabilized by biopolymer complex particles, which have been increasingly recognized for their potential health benefits in protecting against lifestyle-related diseases by the scientific community, industries, and consumers.

Recent progress of Lycium barbarum polysaccharides on intestinal microbiota, microbial metabolites and health: a review.

Intestinal microbiota is symbiotically associated with host health, learning about the characteristics of microbiota and the factors that modulate it could assist in developing strategies to promote human health and prevent diseases. Polysaccharides from Lycium barbarum (LBPs) are found beneficial for enhancing the activity of gut microbiota, as a potential prebiotic, which not only participates in improving body immunity, obesity, hyperlipidemia and systemic inflammation induced by oxidative stress, but also plays a magnificent role in regulating intestinal microenvironment and improving host health and target intestinal effects via its biological activities, as well as gut microbiota and metabolites. To highlight the internal relationship between intestinal microbiota and LBPs, this review focuses on the latest advances in LBPs on the intestinal microbiota, metabolites, immune regulation, intestinal barrier protection, microbiota-gut-brain axis and host health. Moreover, the preparation, structure, bioactivity and modification of LBPs were also discussed. This review may offer new perspective on LBPs improving health of gut and host via intestinal microbiota, and provide useful guidelines for the application of LBPs in the food industry.

Role of thermal and non-thermal drying techniques on drying kinetics and the physicochemical properties of shiitake mushroom.

BACKGROUND: Fresh shiitake mushrooms are rich in nutrients, but have high water content, a fast metabolism after harvest, and deteriorate extremely easily. Therefore, the drying of shiitake mushrooms has become a research direction. However, the role of different drying techniques on shiitake mushroom quality is limited. Therefore, the purpose of this study was to investigate the effect of thermal and non-thermal drying on the drying kinetics, and the physicochemical properties of the end product. RESULTS: Results showed that shiitake mushroom treated with non-thermal drying (vacuum freeze-drying) had an attractive color, low shrinkage, and uniform honeycomb structure, while the drying time was the longest and not conducive to the formation of shiitake mushroom aroma. But shiitake mushroom treated with thermal drying presents an attractive fragrance. In thermal processing technology, compared with hot air convection drying (HAD), infrared hot air convection drying (IRHAD) shortens the drying time by 37.5%, and had the highest oxidation resistance, polysaccharide content and the lowest color change. Relative-humidity drying (RHD) samples had the lowest shrinkage compared with other thermal processing technology. The five polysaccharides exhibited similar preliminary structural characteristics, but the polysaccharides obtained by IRHAD have the highest antioxidant properties. CONCLUSION: These results showed that compared with thermal drying technology, non-thermal drying technology is not suitable for shiitake mushroom processing. In thermal processing technology, IRHAD is a potential drying method to obtain high-quality dried shiitake mushrooms and shiitake mushroom polysaccharide (SMP). However, it is necessary to increase the pretreatment technology to achieve the attractive appearance of non-thermal drying technology. © 2021 Society of Chemical Industry.

Identification of a thermophilic protease-producing strain and its application in solid-state fermentation of soybean meal.

BACKGROUND: Thermophiles can thrive at 50-80 °C and produce some enzymes with special promise for biocatalysis. A thermophilic protease-producing strain YYC4 was isolated from Yunyan cigarette and employed in solid-state fermentation (SSF) of unsterilized soybean meal (SBM). RESULTS: The isolate was identified as Bacillus licheniformis based on appearance of colonies, microscopic observation and 16S rDNA sequencing. After SSF, soluble and crude protein contents in SBM increased from 49.24 to 185.73 g kg-1 and from 404.18 to 479.46 g kg-1 , respectively, under the fermentation conditions of 107 cfu g-1 inoculation of strain YYC4, 1:1.8 (g mL-1 ) SBM to distilled water, 1.2 g kg-1 magnesium sulphate addition, 55 °C and 48 h. During fermentation, pH of the medium increased from 6.30 to 9.09 and protease activity especially neutral protease increased significantly from 13.5 to 181.31 U g-1 . Meanwhile, trypsin inhibitor (TI) activity was decreased from 8.19 to 3.19 mg g-1 . The safety of fermented SBM (FSBM) was verified by acute toxicity animal experiment. Analysis of microbial community in FSBM showed that Bacillus licheniformis YYC4 as a dominant strain inhibited most of the other microorganisms pre-existing in the materials during fermentation. CONCLUSION: Increments of soluble and crude protein by 277.19% and 18.63% and decrement of harmful TI by 61.05% in SBM were achieved using thermophilic SSF by Bacillus licheniformis YYC4, providing a basis for the application of thermophiles in fermentation industry in an environmentally friendly and energy-saving way. © 2021 Society of Chemical Industry.

The selective breeding and mutagenesis mechanism of high-yielding surfactin Bacillus subtilis strains with atmospheric and room temperature plasma.

BACKGROUND: Surfactin, a good biological surfactant, is derived from the metabolites of microorganisms. However, the ability of natural strains to produce surfactin is low, and so the presented study aimed to use a novel mutagenesis technology to increase their yields. RESULTS: Atmospheric and room temperature plasma (ARTP) was used to conduct mutation breeding of Bacillus subtilis CICC 10721, and a mutant strain M45 with a higher surfactin yield of 34.2% and a stable subculture was screened out. From the fermentation kinetics study, it was found that the maximum cell dry weight, maximum growth rate and surfactin synthesis parameters of the mutant strain M45 were all greater than that of the original strain. Scanning electron microscope and laser scanning confocal microscope observations showed that the spore morphology changed after ARTP treating, and the intracellular Ca2+ concentration of the mutant increased. Genome resequencing analysis showed that 66 single nucleotide poymorphism non-synonymous mutation sites occurred in M45, and the identification results of the fermentation broth extract from M45 showed that it is composed of C12 -C16 surfactin. CONCLUSION: ARTP mutagenesis was found to change the morphology of bacteria, membrane permeability and genes related to the synthesis and secretion of surfactin. The present study provides a basis for industrial production of surfactin and an understanding of the mutagenesis mechanism. © 2021 Society of Chemical Industry.

Effect of solid-state fermentation by three different Bacillus species on composition and protein structure of soybean meal.

BACKGROUND: Fermentation efficiency of thermophiles of Bacillus licheniformis YYC4 and Geobacillus stearothermophilus A75, and mesophilic Bacillus subtilis 10 160 on soybean meal (SBM), was evaluated by examining the nutritional and protein structural changes. RESULTS: SBM fermentation by B. licheniformis YYC4, B. subtilis 10 160 and G. stearothemophilus A75 increased significantly the crude and soluble protein from 442.4 to 524.8, 516.1 and 499.9 g kg-1 , and from 53.9 to 203.3, 291.3 and 74.6 g kg-1 , and decreased trypsin inhibitor from 8.19 to 3.19, 2.14 and 5.10 mg g-1 , respectively. Bacillus licheniformis YYC4 and B. subtilis 10 160 significantly increased phenol and pyrazine content. Furthermore, B. licheniformis YYC4 fermentation could produce abundant alcohols, ketones, esters and acids. Surface hydrophobicity, sulfhydryl groups and disulfide bond contents of SBM protein were increased significantly from 98.27 to 166.13, 173.27 and 150.71, from 3.26 to 4.88, 5.03 and 4.21 µmol g-1 , and from 20.77 to 27.95, 29.53 and 25.5 µmol g-1 after their fermentation. Fermentation induced red shifts of the maximum absorption wavelength (λmax ) of fluorescence spectra from 353 to 362, 376 and 361 nm, while significantly reducing the fluorescence intensity of protein, especially when B. subtilis 10 160 was used. Moreover, fermentation markedly changed the secondary structure composition of SBM protein. Analyses by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and atomic force microscopy showed that macromolecule protein was degraded into small-sized protein or peptide during fermentation of SBM. CONCLUSION: Bacillus licheniformis YYC4 fermentation (without sterilization) improved nutrition and protein structure of SBM as B. subtilis 10 160, suggesting its potential application in the SBM fermentation industry. © 2021 Society of Chemical Industry.

Application of ultrasound technology in the field of solid-state fermentation: increasing peptide yield through ultrasound-treated bacterial strain.

BACKGROUND: The increase of peptide yield contributed to reducing the usage of antibiotics in solid-state fermented feed. Ultrasound technology is used in the field of liquid-state fermentation to improve yield of fermented products but has not been utilized in the field of solid-state fermentation (SSF). The main objective of this study was to investigate the feasibility of improving peptide yield in SSF products through ultrasound-treated bacterial strain. RESULTS: The highest peptides content in soybean meal SSF products reached 153.28 mg g-1 , which increased by 15.05% compared with the control. This content value was acquired through treating the bacteria of Bacillus amyloliquefaciens by ultrasound before inoculating into soybean meal under the optimized mode and parameters (simultaneous dual-frequency ultrasound mode, frequency combination of 40/60 kHz, total power density of 40 W L-1 , time of 20 min, pulse-on and pulse-off times of 40 and 60 s, delayed inoculation time of 0 h). Fermenting with ultrasound-treated bacterial strain can effectively increase peptide yield, biomass and protease activity of soybean meal fermented products during the SSF prophase. After treating by ultrasound, the latent phase and logarithmic phase of the bacterial strain shortened by 1 and 3 h while the generation time reduced by 23.64%. In qualitative test of protease activity, diameter ratio (DR) value of ultrasound-treated bacterial cells enlarged by 12.0% compared with the control. CONCLUSION: Peptide yield of soybean meal SSF products can be improved through ultrasound-treated bacterial inoculum, which attributed to the promoting effect of ultrasound treatment on growth activity and protease production capability of bacterial cells. © 2021 Society of Chemical Industry.