Research Progress of ARTP Mutagenesis Technology Based on Citespace Visualization Analysis.

Atmospheric and room temperature plasma (ARTP) mutagenesis technology has been developed rapidly in recent years because of its simple operation, safety, environmental friendliness, high mutation rate, and large mutation library capacity. It has been widely used in traditional fields such as food, agriculture, and medicine, and has been gradually applied in emerging fields such as environmental remediation, bioenergy, and microalgae utilization. In this paper, the Web of Science Core Collection (WOSCC) was used as the data source, and the keywords and core literature of ARTP mutagenesis technology were plotted by citespace software, and the research progress and research hotspots of ARTP mutagenesis technology were analyzed. Through citespace visualization analysis, it is concluded that the country with the largest number of studies is China, the institution with the largest number of studies is Jiangnan University, and the author of the most published papers is Jiangnan University. Through keyword analysis, it is concluded that the most widely used ARTP mutagenesis technology is fermentation-related majors, mainly for biosynthesis and microbial research at the molecular level. Among them, the most widely used microorganisms are Escherichia coli and Saccharomyces cerevisiae.

Preliminary research on the flavor substance and antioxidant capacity of beers produced with baking Qingke.

The addition of baked Qingke improves the flavor profile of beer. In this study, beer was brewed using Qingke baked at various temperatures. The beer produced with Qingke baked at 180 °C achieved the highest sensory score (40/50), an alcohol content of 6.92% (v/v), a total phenolic content of 446.42 mg/L, melanoidin concentration of 98.22 g/L, a color value of 10.88 EBC, and exhibited satisfactory antioxidant activity. Analysis of volatile compounds using HS-SPME-GC-MS revealed 48 compounds, of which esters accounted for 63% and alcohols accounted for 27% of the total content. The flavor profile of the beer varied across different baking temperatures. Pyrazines and aldehydes were predominantly present in samples baked at higher temperatures (T3, T4, and T5). Correlation analysis showed that the baking flavor in the beer was primarily correlated with 2, 5-dimethyl-pyrazine, trimethyl-pyrazine, phenylacetaldehyde, and ethyl 9-decenoate (R > 0.9).

Preparation of layer-assembled W/O/W-type microencapsulated beads and application in solid-state fermentation.

In this study, microcapsule beads-0-3-layers (M-0-3 indicates microencapsulated beads with 0, 1, 2, and 3 layers) were prepared, their properties were measured and characterized, and the effects of M-0-3 on solid-state fermentation were investigated. The results showed that in a liquid environment, the releasing glucoamylase activities of M-0-3 were 55.77%, 47.67%, 45.85%, and 42.87% in 360 h, respectively. In the solid environment, the reducing sugar production efficiency of M-0-3 was 29.84%, 27.72%, 19.16%, and 15.93% in 15 days, respectively. Adding M-0-3 improved the alcohol and reduced sugar content while decreasing the residual starch content of the Jiupei, indicating that adding M-0-3 was beneficial to the solid-state fermentation of Baijiu. Solid-state fermentation simulation experiments illustrated that microcapsule beads play a positive role in the production of Baijiu, enhancing raw material utilization and yield of Baijiu production.

Effects of tea addition on antioxidant capacity, volatiles, and sensory quality of beer.

Green tea has great potential to enhance the quality of beer. In this study, green tea was added at different stages of beer brewing, and evaluated the antioxidant capacity, volatile components, as well as sensory quality. The results showed that the addition of green tea during the start of boiling has great potential for application, and the green tea beer (GTB) had remarkable antioxidant properties (ABTS radical scavenging ability, 8.67 mmol TE/L; DPPH radical scavenging ability, 3.97 mmol TE/L; reducing power, 3.28 mmol TE/L), and an excellent sensory quality (acceptance, 6.09/9). HPLC analysis indicated that the principal phenolics in GTB were catechin and caffeic acid, in addition, the relative amounts of ferulic acid, gallic acid can be used to differentiate between GTB and beer. HS-SPME-GC-MS analyses showed that ethyl caprylate, ethyl nonanoate, ethyl caprate, linalool, and phenethyl alcohol were potentially significant for the aroma profile of GTB.

Preparation of glucoamylase microcapsule beads and application in solid-state fermentation.

BACKGROUND: Baijiu brewing adopts the solid-state fermentation method, using starchy raw materials, Jiuqu as saccharifying fermenting agent, and distilled spirits made by digestion, saccharification, fermentation and distillation. In the late stages of solid-state fermentation of Baijiu, the reduced activity of glucoamylase leads to higher residual starch content in the Jiupei, which affects the liquor yield. The direct addition of exogenous glucoamylase leads to problems such as the temperature of the fermentation environment rising too quickly, seriously affecting the growth of microorganisms. RESULTS: To solve the problem of reduced activity of glucoamylase in the late stage of solid-state fermentation of Baijiu, microcapsule beads (M-B) based on microcapsule emulsion were prepared and the effect of M-B on solid-state fermentation of Baijiu was investigated. The results showed that the release of M-B before and after drying was 53.27% and 25.77% in the liquid state (120 h) and 29.84% and 22.62% in the solid state (15 days), respectively. Adding M-B improved the alcohol by 0.33 %vol and reducing sugar content by 0.51%, reduced the residual starch content by 1.21% of the Jiupei, and had an insignificant effect on the moisture and acidity of the Jiupei. CONCLUSION: M-B have excellent sustained-release properties. The addition of M-B in solid-state fermentation significantly increased the alcohol content, reduced the residual starch content of Jiupei, ultimately improving the starch utilization rate and liquor yield of Baijiu brewing. The preparation of M-B provides methods and approaches for applying other active substances and microorganisms in the brewing of Baijiu. © 2023 Society of Chemical Industry.

Expression and application of aflatoxin degrading enzyme gene in Pichia pastoris.

In this study, three aflatoxin degrading enzyme genes, tv-adtz, arm-adtz and cu-adtz, were heterologously expressed in Pichia pastoris. The protein expression of the enzyme solution was detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis, and the results showed that specific protein bands were detected and the target genes were successfully integrated into Pichia pastoris. The enzyme activities and detoxification efficiency of TV-ADTZ, Arm-ADTZ and Cu-ADTZ crude enzyme solutions were detected, and the highest enzyme activities were up to 3.57, 4.30, and 2.41 U mL-1 , and the highest degradation rates were up to 45.58%, 60.0% and 34.21%, respectively. Arm-ADTZ with the best degradation effect was selected and designed for detoxification application experiments to test its detoxification efficiency of AFB1 in aqueous phase and in the process of moldy ground corn and preparation of DDGS, respectively, and the degradation rates reached 78.94%, 56.48%, and 24.31% after 24 h of reaction, respectively. Thus, it can be seen that the aflatoxin-degrading enzyme gene was successfully integrated into Pichia pastoris and secreted for expression, and the expressed product could effectively degrade AFB1 .

Effect of the addition of mung bean, corn, and sweet potato starch on the properties of konjac gel.

Konjac gel (KG) food is a popular choice among consumers due to its delicious taste, low-calorie content, and ability to provide satiety. The aim of the study was to evaluate the effects of the addition of mung bean starch (MBS), corn starch (CS), and sweet potato starch (SPS) on the water solubility, gel strength, microstructure, and viscosity of KG. The experimental results showed that MBS exhibited the largest amylose content (47.07 ± 1.71%), and SPS had the lowest amylose content (27.92 ± 1.24%). With the increase of starch concentration, the gel strength and viscosity of KG increased, the KG with 3% MBS had higher water solubility and stronger gel strength, and the KG with 3% SPS had better viscosity. In addition, according to the scanning electron microscope, the microstructure of KG without starch was a porous honeycomb, and the network structure of CS/KG was more orderly and uniform. The microstructure of MBS/KG was tightly wrinkled, while the honeycomb structure of SPS/KG was more orderly and the network outline was clearer. The addition of starch could improve the quality of KG, the type of starch used had different effects.

Immobilized glucoamylase based on ZIF-8: Preparation, response surface optimization, characterization.

The glucoamylase@ZIF-8 was prepared using ZIF-8 material as the carrier in this study. The preparation process was optimized by response surface methodology, and the stability of glucoamylase@ZIF-8 was determined. The material was characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The results showed that the optimum preparation process of glucoamylase@ZIF-8 was 1.65 mol 2-methylimidazole, 5.85 mL glucoamylase, 33°C stirring temperature, 90 min stirring time, and 84.0230% ± 0.6006% embedding rate. At 100°C, the free glucoamylase completely lost its activity, whereas the glucoamylase@ZIF-8 still had a retained enzyme activity of 12.0123% ± 0.86158%; at pH 3-6, the highest activity of glucoamylase@ZIF-8 was 95.9531% ± 0.96181%, and about 80% of glucoamylase activity could be retained under alkaline conditions. When the ethanol concentration was 13%, the retained enzyme activity was 7.9316% ± 0.19805%, significantly higher than free enzymes. The Km of glucoamylase@ZIF-8 and free enzyme were 1235.6825 and 80.317 mg/mL, respectively. Vmax was 0.2453 and 0.149 mg/(mL min), respectively. The appearance, crystal strength, and thermal stability of glucoamylase@ZIF-8 were improved after optimization, and they had high reusability.

Effect of Multiple Rounds of Enrichment on Metabolite Accumulation and Microbiota Composition of Pit Mud for Baijiu Fermentation.

Pit mud (PM) is the main component of Baijiu (traditional Chinese liquor), and its microorganisms are the primary sources of the aroma of Chinese strong-flavor Baijiu (SFB). Enrichment plays an important role in the selection of functional microorganisms in PM. Herein, the PM of SFB was submitted to six rounds of enrichment using clostridial growth medium (CGM), and changes in the metabolite accumulation and microbiota composition were evaluated. Based on the metabolite production and microbiota composition, the enrichment rounds were classified as the acclimation stage (round 2), main fermentation stage (rounds 3 and 4), and late fermentation stage (rounds 5 and 6). Species within the genus Clostridium dominated in the acclimation stage (65.84-74.51%). In the main fermentation stage, the dominant microbial groups were producers of butyric acid, acetic acid, and caproic acid, which included Clostridium (45.99-74.80%), Caproicibacter (1.45-17.02%), and potential new species within the order of Oscillataceae (14.26-29.10%). In the late stage of enrichment, Pediococcus dominated (45.96-79.44%). Thus, the main fermentation stage can be considered optimal for the isolation of acid-producing bacteria from PM. The findings discussed herein support the development and application of functional bacteria by bioaugmentation, and contribute to improving the quality of PM and SFB production.

Enhancing the foaming properties of brewer's spent grain protein by ultrasound treatment and glycation reaction.

The denaturation state and relatively poor solubility of brewer's spent grain protein (BSGP) have limited its industrial application. Ultrasound treatment and glycation reaction were applied to improve the structural and foaming properties of BSGP. The results showed that all ultrasound, glycation, and ultrasound-assisted glycation treatments increased the solubility and surface hydrophobicity of BSGP while decreasing its zeta potential, surface tension and particle size. Meanwhile, all these treatments resulted in a more disordered and flexible conformation of BSGP, as observed by CD spectroscopy and SEM. After grafting, the result of FTIR spectroscopy confirmed the covalent binding of -OH between maltose and BSGP. Ultrasound-assisted glycation treatment further improved the free SH and S-S content, which might be due to -OH oxidation, indicating that ultrasound promoted the glycation reaction. Furthermore, all these treatments significantly increased the foaming capacity (FC) and foam stability (FS) of BSGP. Notably, BSGP treated with ultrasound showed the best foaming properties, increasing the FC from 82.22% to 165.10% and the FS from 10.60% to 131.20%, respectively. In particular, the foam collapse rate of BSGP treated with ultrasound-assisted glycation was lower than that of ultrasound or traditional wet-heating glycation treatment. The enhanced hydrogen bonding ability and hydrophobic interaction between protein molecules caused by ultrasound and glycation might be responsible for the improved foaming properties of BSGP. Thus, ultrasound and glycation reactions were efficient methods for producing BSGP-maltose conjugates with superior foaming properties.

Preparation and characterization of glucoamylase microcapsules prepared by W/O/W type complex coacervation freeze drying.

Glucoamylase was often used in the brewing industry but was unstable to several environmental factors and reacted quickly to produce fermentable sugar, which limited its applications. Microencapsulation could effectively overcome the drawbacks. This study evaluated the feasibility of the preparation of glucoamylase microcapsules (GM) using W/O/W complex coacervation-freeze-drying method. The parameters of the microcapsules were optimized by the response surface optimization design: core-wall ratio at 1:1, wall-material concentration at 8%, and coagulation time for 20 min. Under current condition, the final microencapsulation efficiency reached 85.64 ± 1.60%. Glucoamylase could be slowly released for more than 96 h in the liquid state, and could react slowly for more than 336 h in the solid state. The optimized GM were incubated for 1 h, and the relative enzyme activity was better than that of free glucoamylase under high temperature conditions. The water capacity, solubility, morphology, differential scanning calorimetry, and Fourier transform infrared spectroscopy were conducted. Glucoamylase exhibited good sustained release characteristics. The microcapsules were more resistant to environmental stimuli and showed stronger robustness after optimization. PRACTICAL APPLICATION: Saccharification enzymes are often used in the winemaking industry, and direct addition will cause the fermentation process to heat up too quickly, resulting in the inactivation of microorganisms and saccharification enzymes, affecting the efficiency of saccharification enzymes. Therefore, microcapsules are used to encapsulate the saccharification enzyme, and its efficacy is slowly released for a long time during the fermentation process.

FT-IR combined with chemometrics in the quality evaluation of Nongxiangxing baijiu.

Recently, there has been an increasing demand for developing a reliable method to assess the quality of liquor in the baijiu industry quickly and accurately. The present study sought to establish a strategy for rapid quantitative analysis of the primary flavor components in Nongxiangxing baijiu. Under the experimental conditions, 7 of the 10 major flavor components in Nongxiangxing baijiu could be quantified effectively, such as ethyl butyrate (R2p = 0.9942), ethyl lactate (R2p = 0.9438), n-butanol (R2p = 0.9048), isobutanol (R2p = 0.9696), acetic acid (R2p = 0.9600), butyric acid (R2p = 0.8448), caproic acid (R2p = 0.9971). This result indicates that FT-IR combined with quantitative chemometric modeling could be a potential approach for rapid quality assessment of Nongxiangxing baijiu. Overall, this study provides a theoretical basis for subsequent related studies on Nongxiangxing baijiu.

Research progress of glucoamylase with industrial potential.

Glucoamylase is one of the most widely used enzymes in industry, but the development background and existing circumstances of industrial glucoamylase were not described by published articles. CiteSpace, a powerful tool for bibliometric, was used to analyze the past, existing circumstances, and trends of a professional field. In this study, 1820 Web-of-Science-indexed articles from 1991 to 2021 were collected and analyzed by CiteSpace. The research hotspots of industrial glucoamylase, like glucoamylase strain directional improvement, Aspergillus niger glucoamylase, glucoamylase immobilization, application of glucoamylase in ethanol production, and "customized production" of porous starch, were found by analyzing countries, institutions, authors, keywords, and references of articles. PRACTICAL APPLICATIONS: The research progress of glucoamylase with industrial potential was analyzed by CiteSpace, and a significant research direction of glucoamylase with industrial potential was found. This is helpful for academic and corporate audiences to understand the current situation of glucoamylase with industrial potential and carry out follow-up works.

Improvement of Multiple-Stress Tolerance and Ethanol Production in Yeast during Very-High-Gravity Fermentation by Supplementation of Wheat-Gluten Hydrolysates and Their Ultrafiltration Fractions.

The effects of wheat-gluten hydrolysates (WGH) and their ultrafiltration fractions on multiple-stress tolerance and ethanol production in yeast during very-high-gravity (VHG) fermentation were examined. The results showed that WGH and WHG-ultrafiltration-fraction supplementations could significantly enhance the growth and viability of yeast and further improve the tolerance of yeast to osmotic stress and ethanol stress. The addition of MW < 1 kDa fractions led to 51.08 and 21.70% enhancements in cell-membrane integrity, 30.74 and 10.43% decreases in intracellular ROS accumulation, and 34.18 and 26.16% increases in mitochondrial membrane potential (ΔΨm) in yeast under osmotic stress and ethanol stress, respectively. Moreover, WGH and WHG-ultrafiltration-fraction supplementations also improved the growth and ethanol production of yeast during VHG fermentation, and supplementation with the <1 kDa fraction resulted in a maximum biomass of 16.47 g/L dry cell and an ethanol content of 18.50% (v/v) after VHG fermentation.

Wheat gluten hydrolysates separated by macroporous resins enhance the stress tolerance in brewer's yeast.

Wheat gluten hydrolysates (WGH) were used to examine their adsorption-desorption kinetics and thermodynamics characteristics on six macroporous resins, and their effects on the stress tolerance in brewer's yeast. Results showed that the pseudo second-order kinetics, Langmuir and Freundlich model could illuminate the adsorption mechanism, and the adsorption process was physical, spontaneous and exothermic. The 40% ethanol fraction separated by XAD-16 resin improved significantly the ethanol tolerance and the viability of brewer's yeast, while the 0% ethanol fraction separated by XAD-16 resin increased obviously the osmotic stress tolerance and the viability of brewer's yeast. Results from scanning electron microscopy showed that both these WGH fractions could increase budding rate and maintain normal morphology of yeast cells under various environmental stress. Thus, WGH separated by macroporous resin could be used in high gravity brewing to enhance the ethanol and osmotic stress tolerance in brewer's yeast.

Peptide (Lys-Leu) and amino acids (Lys and Leu) supplementations improve physiological activity and fermentation performance of brewer's yeast during very high-gravity (VHG) wort fermentation.

Lys and Leu were generally considered as the key amino acids for brewer's yeast during beer brewing. In the present study, peptide Lys-Leu and a free amino acid (FAA) mixture of Lys and Leu (Lys + Leu) were supplemented in 24 °P wort to examine their effects on physiological activity and fermentation performance of brewer's yeast during very high-gravity (VHG) wort fermentation. Results showed that although both peptide Lys-Leu and their FAA mixture supplementations could increase the growth and viability, intracellular trehalose and glycerol content, wort fermentability, and ethanol content for brewer's yeast during VHG wort fermentation, and peptide was better than their FAA mixture at promoting growth and fermentation for brewer's yeast when the same dose was kept. Moreover, peptide Lys-Leu supplementation significantly increased the assimilation of Asp, but decreased the assimilation of Gly, Ala, Val, (Cys)2, Ile, Leu, Tyr, Phe, Lys, Arg, and Pro. However, the FAA mixture supplementation only promoted the assimilation of Lys and Leu, while reduced the absorption of total amino acids to a greater extent. Thus, the peptide Lys-Leu was more effective than their FAA mixture on the improvement of physiological activity, fermentation performance, and nitrogen metabolism of brewer's yeast during VHG wort fermentation.