Fermentation Temperature Research Articles

Characterization of color, metabolites and microbial community dynamics of doubanjiang during constant temperature fermentation

This study aimed to elaborate the effect of temperature on doubanjiang fermentation. Two batches of constant-temperature groups were prepared and their physicochemical parameters, color formation, metabolites and microbial community dynamics during fermentation were determined and compared with those of natural temperature fermentation group. The results showed that fermentation at 40 °C could accelerate the accumulation of amino nitrogen, reducing sugar, amino acids, organic acids and various volatile metabolites while it was able to inhibit the growth of conditionally pathogenic bacteria, such as Klebsiella and Salmonella. However, high concentrations of total acids and biogenic amines, protrusive burnt flavor and darker color were observed in constant temperature fermentation, which were unfavorable for doubanjiang quality. Higher fermentation temperature lowered the diversity of bacterial community and favored the growth of Bacillus genus. The correlation between key microbial genera and doubanjiang quality indexes were significantly different among different temperatures. This study would deep our understanding of the roles of temperature ondoubanjiangfermentation.

High-temperature fermentation of corn stover for biodiesel production using Candida tropicalis with enhanced lipid accumulation: A new strategy for breeding thermotolerant biodiesel-production strains

Efficient biodiesel production from biomass is essential for the green-oriented energy transition. The current incongruity between fermentation temperature and microbial thermotolerance is one of the key factors restricting biodiesel production, and it is difficult to solve this problem relying only on conventional microbial characterization and breeding methods. We propose a strategy to solve the corn stover cellulose utilization problem by developing thermotolerant biodiesel-production yeast strains. Candida tropicalis was initially improved by adaptive laboratory evolution and then mutated by atmospheric and room-temperature plasma mutagenesis to obtain a thermotolerant strain capable of growing at temperatures up to 45 °C. Two rounds of fluorescence-activated cell sorting were used to select high lipid content cells, which resulted in a 16.8% increase in lipid accumulation capacity compared to the original cells. The simultaneous saccharification fermentation of the generated strain with pretreated corn stover at 44 °C yielded a lipid generation efficiency of 86.2 ± 2 mg/g. This study provides a new method and an alternative strain for the selection and breeding of high-thermotolerance and high biodiesel-production yeasts and offers a feasible strategy for lignocellulosic fermentation for biodiesel production at elevated temperatures using the new industrial strain.

The Optimisation of Bitter Gourd-Grape Beverage Fermentation Using a Consolidated Response Surface Methodology (RSM) and Artificial Neural Network (ANN) Approach.

The present study adopted a response surface methodology (RSM) approach validated by artificial neural network (ANN) models to optimise the production of a bitter gourd-grape beverage. Aset of statistically pre-designed experiments were conducted, and the RSM optimisation model fitted to the obtained data, yielding adequately fit models for the monitored control variables R2 values for alcohol (0.79), pH (0.89), and total soluble solids (TSS) (0.89). Further validation of the RSM model fit using ANN showed relatively high accuracies of 0.98, 0.88, and 0.82 for alcohol, pH, and TSS, respectively, suggesting satisfactory predictability and adequacy of the models. A clear effect of the optimised conditions, namely fermentation time at (72 h), fermentation temperature (32.50 and 45.11 °C), and starter culture concentration (3.00 v/v) on the total titratable acidity (TTA), was observed with an R2 value of (0.40) and RSM model fit using ANN overall accuracy of (0.56). However, higher TTA values were observed for samples fermented for 72 h at starter culture concentrations above 3 mL. The level of 35% bitter gourd juice was optimised in this study and was considered desirable because the goal was to make a low-alcohol beverage.

Determination and Modeling of Proximate and Thermal Properties of De-Watered Cassava Mash (Manihot esculenta Crantz) and Gari (Gelatinized cassava mash) Traditionally Processed (In Situ) in Togo

The roasting process of Gari (Gelatinized cassava mash), a shelf-stable cassava product, is energy-intensive. Due to a lack of information on thermal characteristics and scarcity/rising energy costs, heat and mass transfer calculations are essential to optimizing the traditional gari procedure. The objective of this study was to determine the proximate, density, and thermal properties of traditionally processed de-watered cassava mash and gari at initial and final processing temperatures and moisture contents (MCwb). The density and thermal properties were determined using proximate composition-based predictive empirical models. The cassava mash had thermal conductivity, density, specific heat capacity, and diffusivity of 0.34 to 0.35 W m−1 °C−1, 1207.72 to 1223.09 kg m−3, 2849.95 to 2883.17 J kg−1 °C, and 9.62 × 10−8 to 9.76 × 10−8 m2 s−1, respectively, at fermentation temperatures and MCwb of 34.82 to 35.89 °C and 47.81 to 49%, respectively. The thermal conductivity, density, specific heat capacity and diffusivity of gari, ranged from 0.27 to 0.31 W m−1 °C−1, 1490.07 to 1511.11 kg m−3, 1827.71 to 1882.61 J kg−1 °C and 9.64 × 10−8 to 1.15 × 10−8 m2 s−1, respectively. Correlation of all the parameters was achieved, and the regression models developed showed good correlation to the published models developed based on measuring techniques.

Understanding the relationship between tropical fruit aroma, acceptance, and emotional response in chardonnay wines

Tropical fruit aromas are prominent in many white wines. The purpose of this work was to determine if winemaking practices could impact the tropical fruit aromas in the Chardonnay wines and how those aroma differences influenced wine consumers acceptance and emotional responses. Four treatments were tested at varying fermentation temperature gradients and skin contact times: control fermentation at 13 °C with no skin contact (Control), fermentation at 13 °C with 18 h of skin contact (SC), fermentation temperature gradient by time (20 °C for 4 days then reduced to 13 °C) with no skin contact (FG), fermentation temperature gradient by time with 18 h of skin contact (SCFG). Acceptance, using a 7-point hedonic scale, showed there was not a significant difference between treatments. Emotional response, using a 5-point Rate-All-That-Apply (RATA) scale, showed significant differences for ‘calm’ and ‘disgusted’ emotions. Check-all-that-apply (CATA) for aroma descriptors showed that Control is described using aromas of passionfruit, lychee, and pome fruit; SC had aromas of grapefruit and floral; FG was described as having melon, lychee, and pineapple aromas; and SCFG was described with aromas of lemon/lime, mango, and guava. Positive emotions were associated with fruity aromas in the wines, although no difference in acceptance was found. Winemaking treatments impacted the aroma profile of chardonnay wine, with tropical aromas evoking positive emotions in consumers. The relationship between specific aromas and consumers emotion responses can be an important tool to understand the factors behind a wine’s success or lack thereof. Moreover, it can help with the creation of new wine products.

Optimization of Fermentation Conditions and Product Identification of a Saponin-Producing Endophytic Fungus.

Some fungal endophytes isolated from P. ginseng may present a new method of obtaining saponins. This experiment aimed to optimize the total saponin yield produced through in vitro fermentation by an endophytic fungus and analyze its saponin species in the fermented extract. Fermentation protocols were optimized with a uniform design and verified through regression analysis to maximize the total saponin yield. The saponin types under optimal fermentation conditions were then identified and analyzed using Liquid Chromatography-Mass Spectrometry. The Trametes versicolor strain NSJ105 (gene accession number: OR144428) isolated from wild ginseng could produce total saponins. The total saponin yield could be increased more than two-fold through the optimization of fermentation conditions. The concentration of the total saponins achieved by the verified protocol 105-DP was close to the predicted value. The fermentation conditions of the 105-DP protocol were as follows: potato concentration 97.3 mg/mL, glucose concentration 20.6 mg/mL, inoculum volume 2.1%, fermentation broth pH 2.1, fermentation temperature 29.2 °C, and fermentation time 6 d. It was detected and analyzed that the fermented extract of 105-DP contained the ginsenosides Rf and Rb3. The endophytic fungus Trametes versicolor strain NSJ105 has potential application value in saponin production.

Optimizing the degradation of aflatoxin B1 in corn by Trametes versicolor and improving the nutritional composition of corn.

Corn, being an important grain, is prone to contamination by aflatoxin B1 (AFB1 ), and AFB1 -contaminated corn severely endangers the health of humans and livestock. Trametes versicolor, a fungus that can grow in corn, possesses the ability to directly degrade AFB1 through its laccase. This study aimed to optimize the fermentation conditions for T. versicolor to degrade AFB1 in corn and investigate the effect of T. versicolor fermentation on the nutritional composition of corn. AFB1 -contaminated corn was used as the culture substrate for T. versicolor. A combination of single-factor experiments and response surface methodology was employed to identify the optimal conditions of AFB1 degradation. The optimal conditions of AFB1 degradation were as follows: 9 days of fermentation, a fermentation temperature of 26.7 °C, a moisture content of 70.5% and an inoculation amount of 4.9 mL (containing 51.99 mg of T. versicolor mycelia). With the optimal conditions, the degradation rate of AFB1 in corn could reach 93.01%, and the dry basis content of protein and dietary fiber in the fermented corn was significantly increased. More importantly, the lysine content in the fermented corn was also significantly increased. This is the first report that direct fermentation of AFB1 -contaminated corn by T. versicolor not only efficiently degrades AFB1 but also improves the nutritional composition of corn. These findings suggest that the fermentation of corn by T. versicolor is a promising, environmentally friendly and efficient approach to degrade AFB1 and improve the nutritional value of corn. © 2023 Society of Chemical Industry.

Optimization of the Fermentation Conditions of Huaniu Apple Cider and Quantification of Volatile Compounds Using HS-SPME-GC/MS.

The fermentation process and composition of volatile compounds play a crucial role in the production of Huaniu apple cider. This study aimed to optimize the fermentation conditions of Huaniu apple cider and quantify its volatile compounds using headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC/MS). The optimal fermentation parameters were determined using response surface methodology (RSM). The optimal fermentation temperature was 25.48 °C, initial soluble solids were 18.90 degrees Brix, inoculation amount was 8.23%, and initial pH was 3.93. The fermentation rate was determined to be 3.0, and the predicted value from the verification test was 3.014. This finding demonstrated the excellent predictability of a RSM-optimized fermentation test for Huaniu apple cider, indicating the reliability of the process conditions. Moreover, the analysis of volatile compounds in the optimized Huaniu cider identified 72 different ingredients, including 41 esters, 16 alcohols, 6 acids, and 9 other substances. Notably, the esters exhibited high levels of ethyl acetate, ethyl octanoate, and ethyl capricate. Similarly, the alcohols demonstrated higher levels of 3-methyl-1-butanol, phenethylethanol, and 2-methyl-1-propanol, while the acids displayed increased concentrations of acetic acid, caproic acid, and caprylic acid. This study provides the essential technical parameters required for the preparation of Huaniu apple cider while also serving as a valuable reference for investigating its distinct flavor profile.

In situ produced exopolysaccharides by Bacillus coagulansIBRC-M 10807 and its effects on properties of whole wheat sourdough.

This study aimed to investigate in situ exopolysaccharides (EPSs) production by Bacillus coagulans IBRC-M 10807 under different fermentation conditions to improve the technical-functional properties of whole wheat flour sourdough and obtain high-quality products. For this purpose, the effectiveness of four efficient factors including B. coagulans (8 Log CFU/g), FOS (0%, 2.5%, and 5% based on flour weight), fermentation temperature (30, 35, and 40°C), and fermentation time (12, 18, and 24 h) was investigated on the production of functional sourdough. Our work focused on optimizing probiotic sourdough by investigating probiotic viability, pH, total titratable acidity, antioxidant properties, and EPS measurement. The first optimal formulation for maximized production of the in situ EPSs by the numerical optimization included FOS 0%, B. coagulans IBRC-M 10807 8 Log CFU/g, fermentation temperature of 30°C, and fermentation time of 12 h. In this case, EPSs was 59.28 mg/g and probiotic was 10.99 Log CFU/g. The second optimal formula by considering the highest viability of probiotic together with EPS production was determined as FOS 4.71%, B. coagulans IBRC-M 10807, 8 Log CFU/g, fermentation temperature of 30°C, and fermentation time of 20 h. The predicted amount of the EPSs and probiotic viability via the second formulation were 54.4 mg/g and 11.18 Log CFU/g, respectively. Analyses of optimal sourdough using FTIR, SEM, and DSC revealed that FOS and probiotics significantly reduced the enthalpy of amylopectin retrogradation and delayed it compared to other samples. Therefore, improving the final product's technological capabilities and shelf life can be credited with potential benefits.

Optimization of Some Fermentation Conditions for Bioethanol Production from Yam Peels (Dioscorea rotundata) Using Box-Behnken Design (BBD)

Aim: The aim of this research was to optimize the production of bioethanol from a select second generation feedstock (yam peels).
 Methodology: Bioethanol was produced from yam peels using Box Behnken Design (BBD). The independent variables selected for optimization of bioethanol yield were; fermentation temperature (˚C), fermentation time (hours) and yeast concentration (%w/v). A set of 17 experiments were considered by design expert software. All experiments were run in triplicates. Test for bioethanol was carried out using acidified potassium dichromate method and absorbance was taken using a spectrophotometer at 600nm.
 Results: From the experiments carried out above, the optimum conditions under which the highest bioethanol (yield%) was produced were a fermentation temperature of 30̊C, yeast concentration of 5.50%w/v and fermentation time of 96hours under which a bioethanol yield of 45.79% was produced.
 Conclusion: Yam peels may therefore have the potentials to serve as substrates for bioethanol production rather than using food crops such as sugarcane juice and cassava flesh which may lead to food shortages and crisis especially is developing countries such as Nigeria.

Effects of fermentation chamber temperature on microbes and quality of cigar wrapper tobacco leaves.

The natural fermentation of cigar tobacco leaves usually utilizes natural temperature and humidity for fermentation. Cigars produced in China are often fermented in winter, and the low environmental temperatures can lead to slow heating of the tobacco stack, affecting the cigar tobacco leaves quality. This study aimed to determine the minimum chamber temperature required to initiate the process of fermentation for cigar tobacco leaves and to explore the impact of temperature on the microbial community of tobacco leaves. Here, the cigar variety "Dexue 1" were subjected to stacking fermentation under three temperature parameters (20 ℃, 27 ℃, 34 ℃). With an increase in environmental temperature, the temperature inside the stack of cigar leaves increased significantly, the protein, total sugar, starch, and total alkaloid content in fermented tobacco leaves decreased, and the aroma components and amino acid content increased. Microbial richness and community diversity associated with fermented tobacco were highest at chamber temperatures of above 27 ℃. The relative abundance of Chryseobacterium and Rhodococcus was significantly negatively correlated with protein, alkaloids, total sugar, and starch, and positively correlated with amino acids and aroma components. Chryseobacterium and Rhodococcus may be responsible for the degradation of macromolecular substances and the conversion of favorable aromatic substances, thus improving the tobacco leaves quality. This study demonstrated that increasing the fermentation chamber temperature above 27 ℃ was conductive to raising the inner-stack temperature, increased microbial diversity and aromatic quality, reduced the strength and irritation, and extremely enhanced the overall quality of fermented cigar tobacco leaves. KEY POINTS: • The environmental temperature of the fermentation chamber has a significant impact on the quality of tobacco • Temperature > 27 ℃ can initiate the process of cigar tobacco leaves fermentation and increase inner-stack temperature and microbial diversity and abundance • Chryseobacterium and Rhodococcus may be related to the degradation of macromolecular substances and the transformation of aromatic substances, thereby improving the quality of tobacco leaves.

Bacterial diversity and physicochemical properties of low-salt shrimp paste fermented at different temperatures

Low-salt shrimp paste (LSP) is a new emerging shrimp paste. The specific objective of this research was to investigate the effect of fermentation temperature on the physicochemical properties and bacterial communities in LSP. The results indicated that the content of total volatile basic nitrogen (TVB-N), amino acid nitrogen (AAN), and TCA-soluble peptide in the LSP fermented at different temperatures (10 °C, 15 °C, 20 °C and 25 °C) all exhibited an increasing trend with increasing temperature, while the content of malondialdehyde (MDA) showed a trend of first rising and then falling. High-throughput sequencing showed that the Firmicutes, Actinobacteria, Proteobacteria, Bacteroidetes and Staphylococcus were dominant in LSP fermented at 10 °C, while Firmicutes and Tetragenococcus were dominant in LSP fermented at 25 °C. Furthermore, correlation analysis suggested that IIumatobacter, Staphylococcus and Mycobacterium were positively correlated with the content of TCA-soluble peptide, TVB-N and AAN, while negatively correlated with pH in LSP fermented at 10 °C. Tetragenococcus, Ensifer, Acinetobacter and Weissella were positively correlated with most of the physicochemical properties in LSP fermented at 25 °C. In conclusion, fermentation temperature could significantly affect the physicochemical properties and the bacterial community in LSP. These findings provide a theoretical reference for advancing the thermostatic fermentation of commercial LSP.

Comparative analyses of milk and water kefir: Fermentation temperature, physicochemical properties, sensory qualities, and metagenomic composition

Milk and water kefir have been attractive to consumers as health-promoter fermented beverages. Although both are called “kefir”, they differ in physicochemical and microbial properties. In this study, we aimed to compare milk and water kefir in terms of biomass increase, physicochemical properties, sensory qualities, and microbial loads incubated at different incubation temperatures (20 °C, 25 °C, and 30 °C) to mimic approximate room temperatures in various seasons. Additionally, the microbial diversity of the grains was compared through metagenomic analysis. The results showed that the biomass increase, physicochemical properties, and sensory analysis of milk kefir grains depended on the fermentation temperature (p < 0.05); while in general, water kefir was not affected by the fermentation temperature. The highest total dry matter, protein, and fat content, and the least acidity were recorded at 20 °C in milk kefir drinks (p < 0.05). Around 8 and 6 log CFU/ml microorganism loads (Lactobacillus spp., Lactococcus spp., yeasts, total aerobe, and anaerobe bacteria) were recorded for milk and water kefir drinks, respectively, regardless of the temperature. Bifidobacterium load was recorded as the lowest for both kefir drinks. The dominant species of bacteria and yeasts were determined as Lactobacillus parakefiri (21.28%) and Geotricum silvicola (65.10%) in milk kefir grain, and Lactobacillus nagelii (95.69%) and Dekkera bruxellensis (95.24%) in water kefir grain, respectively. The study showed that milk and water kefir differ in terms of physicochemical, sensory, and microbial aspects. Despite its low protein content, water kefir would be a probiotic substitute for milk kefir due to its probiotic features for vegans or people with lactose intolerance.

Secretory expression and fermentation optimization for extracellular production of pullulanase in Vibrio natriegens

Pullulanase is a starch debranching enzyme, which is difficult in secretory expression due to its large molecular weight. Vibrio natriegens is a novel expression host with excellent efficiency in protein synthesis. In this study, we achieved secretory expression of the full-length pullulanase PulA and its truncated mutant PulN2 using V. natriegens VnDX strain. Subsequently, we investigated the effects of signal peptide, fermentation temperature, inducer concentration, glycine concentration and fermentation time on the secretory expression. Moreover, the extracellular enzyme activities of the two pullulanases produced in V. natriegens VnDX and E. coli BL21(DE3) were compared. The highest extracellular enzyme activity of PulA and PulN2 in V. natriegens VnDX were 61.6 U/mL and 64.3 U/mL, which were 110% and 62% that of those in E. coli BL21(DE3), respectively. The results indicated that V. natriegens VnDX can be used for secretory expression of the full-length PulA with large molecular weight, which may provide a reference for the secretory expression of other large molecular weight proteins in V. natriegens VnDX.

Optimization of the Process for Green Jujube Vinegar and Organic Acid and Volatile Compound Analysis during Brewing.

Healthy fruit vinegar has become very popular recently in China. This study aimed to produce fruit vinegar with a good taste, high nutritional value, and strong functional properties from green jujube. This study investigated the optimization of the process for green jujube vinegar using response surface methodology. The optimum fermentation parameters for green jujube vinegar were determined as follows: initial alcoholicity 6%, acetobacter 8%, fermentation temperature 32 °C, and time 7 d. The organic acids of the optimized sample were evaluated by HPLC, and the volatile substances were identified and analyzed by HS-SPME and GC-MS during the fermentation and aging of the green jujube vinegar. The results showed that the variation trends of the different organic acids during the making of the green jujube vinegar were significantly different. Organic acids are the key flavor compounds of green jujube vinegar, and their changes were mainly attributed to microbial metabolism. In particular, the green jujube vinegar stood out in terms of volatile aroma compounds, including a total of 61 volatile compounds whose major components were acetic acid, isoamyl acetate, ethyl acetate, 3-hydroxy-2-butanone, methyl palmitate, and ethanol. The results can provide theoretical support for the production of green jujube vinegar.

Sucrose Concentration and Fermentation Temperature Impact the Sensory Characteristics and Liking of Kombucha.

Kombucha is a fermented tea beverage consumed for its probiotics and functional properties. It has a unique sensory profile driven by the properties of tea polyphenols and fermentation products, including organic acids. Fermentation temperature and sucrose content affect the fermentation process and the production of organic acids; yet less is known about their impacts on the sensory profile and consumer acceptance. Thus, we aimed to examine the impact of sucrose concentration and fermentation temperature on sensory attributes and liking. For this study, kombucha tea was fermented at three different concentrations of sucrose and fermented at two temperatures for 11 days. Fermentation was monitored by pH, brix, and titratable acidity, and consumers (n = 111) evaluated the kombucha for sensory attributes and overall liking. The fermentation temperature resulted in significant differences in titratable acidity, with higher temperatures producing more organic acids, resulting in higher astringency, and suppressed sweetness. The lower fermentation was reported as significantly more liked, with no difference in liking between the 7.5% and 10% sucrose kombucha samples. Fermentation temperature had the greatest impact on the sensory profile rather than sucrose concentration, which had a greater effect on the fermentation rate and production organic acids.

Optimization of Fermentation Process for Apricot Vinegar

To study the optimal fermentation conditions of Prunus armeniaca L. (apricot), single factor experiments and orthogonal experiments were implemented. The experimental results demonstrate that the optimum alcoholic fermentation conditions are: sugar degree a 9%, inoculation quantity of yeast at 0.7%, fermentation temperature at 30 ºC. The alcohol degree could reach 7.56%; the optimum acetic fermentation conditions are: alcohol degree at 7%, inoculation quantity of acetic acid bacillus at 0.8%, fermentation temperature at 32 ºC, fermentation time at 7 days, and the total acid content could be obtained as 6.78 g/100 mL. Under such conditions, the fruit vinegar has rich Prunus armeniaca L. flavor and pure taste.

Shotgun metagenomics and physicochemical insights into the effects of temperature on bacterial community and related metabolism in fermented skates

Fermented skate, an indigenous fermented fish, is traditionally produced by spontaneous fermentation in Korea, wherein the fermentation temperature plays a vital role. To understand the effect of fermentation temperature on fermented skate, this study investigated the impact of fermentation temperature on the quality characteristics and microbial diversity of skates during fermentation at 25 and 10 °C. The physicochemical properties of the skate, including the pH, color, textural profiles, trimethylamine nitrogen, total volatile base nitrogen, ammonia nitrogen, and urea contents, were determined during weeks 1 and 2 of fermentation at 10 and 25 °C, respectively. In addition, the microbial diversity of the fermented skates at 25 and 10 °C was compared by shotgun metagenomic sequencing. This study also examined the correlation between physicochemical and metagenomics. At the genus level, Paenalcaligenes, Clostridium, and Bacillus were the predominant bacteria in the skate sample fermented at 25 °C, whereas the dominant genera in the skate fermented at 10 °C were Psychrobacter and Sporosarcina. At the species level, Psychrobacter sp. DAB_AL43B and Psychrobacter arcticus were predominant species in the skate fermented at 10 °C, whereas Paenalcaligenes hominis and Erysipelothrix rhusiopathiae were predominant species in skate fermented at 25 °C. Based on these results, it was observed that the fermentation temperature affected the fermentation period and quality and the bacterial abundance at the endpoint of fermentation in the fermented skate. These results can serve as a valuable resource to produce high-quality fermented skates at appropriate fermentation temperature.

PRODUCTION AND CHARACTERIZATION OF DEXTRAN BIOSYNTHESIZING GLUCOSYLTRANSFERASE FROM L. MESENETEROIDES KIBGE-IB40

Exploration of biodiversity led towards the development of commercially important biological metabolites. This study focus on the molecular characterization of dextransucrase biosynthezing lactic acid bacterial strain, L. mesenteroides KIBGE-IB40. Fermentation system was designed to optimize the crucial production parameters of the biosynthesis of dextransucrase by L. mesenteroides. Data acquired from the experimental analysis revealed a significant increase of about 1.69-fold in enzyme titer from 67.13 DSU/ml to 114.04 DSU/ml. The optimum fermentation conditions were found to be fermentation time, 18 hours; fermentation temperature, 25°C; fermentation pH, 7.5. Structural analysis of purified dextran was performed. The morphological analysis of dextran by SEM revealed a porous structure of the polysaccharide. FTIR analysis demonstrates the functional group analysis of the polymer. The significant increase in dextransucrase yield demonstrates the crucial impact of fermentation conditions on the metabolic properties of microbial cells. The obtained results demonstrate a practical approach for the commercial application of L. mesenteroides KIBGE-IB40 dextransucrase in food and other industrial sectors.

Microbial Diversity of Anaerobic-Fermented Coffee and Potential for Inhibiting Ochratoxin-Produced Aspergillus niger.

Coffee flavor considerably depends on the fermentation process, with contributing factors including fermentation temperature, oxygen concentration, and microbial diversity. Efficient controlling of the fermentation can improve the quality of coffee beverages. Therefore, several studies on coffee fermentation processes have been conducted in various regions. The objective of this study was to assess the microbial diversity of coffee beans undergoing anaerobic fermentation at various temperatures (4 °C or 37 °C) and fermentation durations (12 h or 36 h) using full-length 16S rRNA sequencing. This analysis aimed to evaluate the inhibitory effects of the fermented metabolites against ochratoxin-producing Aspergillus niger. From our results, Acetobacter was identified as the dominant microbial community at higher fermentation temperatures, whereas Leuconostoc and Gluconobacter were the dominant genera at lower temperatures. However, at lower temperatures, changes in microbial communities were relatively slow. This study expands our knowledge of the microbial diversity involved in the anaerobic fermentation of coffee beans in Taiwan. The findings of this study can be used in future research to cultivate microorganisms linked to the quality and improve the quality of coffee beverages through fermentation.