Effect of salt-tolerant yeast of Candida versatilis and Zygosaccharomyces rouxii on the production of biogenic amines during soy sauce fermentation

Metabolomics analysis of salt tolerance of Zygosaccharomyces rouxii and guided exogenous fatty acid addition for improved salt tolerance

BACKGROUND

Zygosaccharomyces rouxii plays an irreplaceable role in the manufacture of traditional fermented foods, which are produced in a high-salt environment. However, there is little research on strategies for improving salt tolerance of Z. rouxii.

RESULTS

In this study, metabolomics was used to reveal the changes in intracellular metabolites under salt stress, and the results show that most of the carbohydrate contents decreased, the contents of xanthohumol and glycerol increased (fold change 4.07 and 5.35, respectively), while the contents of galactinol, xylitol and d-threitol decreased (fold change -9.43, -5.83 and -3.59, respectively). In addition, the content of four amino acids and six organic acids decreased, while that of the ten nucleotides increased. Notably, except for stearic acid (C18:0), all fatty acid contents increased. Guided by the metabolomics results, the effect of addition of seven exogenous fatty acids (C12:0, C14:0, C16:0, C18:0, C16:1, C18:1, and C18:2) on the salt tolerance of Z. rouxii was analyzed, and the results suggested that four exogenous fatty acids (C12:0, C16:0, C16:1, and C18:1) can increase the biomass yield and maximum growth rate. Physiological analyses demonstrated that exogenous fatty acids could regulate the distribution of fatty acids in the cell membrane, increase the degree of unsaturation, improve membrane fluidity, and maintain cell integrity, morphology and surface roughness.

CONCLUSION

These results are applicable to revealing the metabolic mechanisms of Z. rouxii under salt stress and screening potential protective agents to improve stress resistance by adding exogenous fatty acids. © 2022 Society of Chemical Industry.

Ameliorative Effect of Chitosan Oligosaccharides on Hepatic Encephalopathy by Reshaping Gut Microbiota and Gut-Liver Axis

This study investigated the influence of chitosan oligosaccharides (COSs) on a thioacetamide-induced hepatic encephalopathy (HE) Wistar rat model. COS treatment statistically reduced the false neurotransmitters and blood ammonia in HE rats, along with the suppression of oxidative stress and inflammation. The disbalanced gut microbiota was detected in HE rats by 16S rDNA sequencing, but the abundance alterations of some intestinal bacteria at either the phylum or genus level were at least partly restored by COS treatment. According to metabolomics analysis of rat feces, six metabolism pathways with the greatest response to HE were screened, several of which were remarkably reversed by COS. The altered metabolites might serve as a bridge for the alleviated HE rats treated with COS and the enhanced intestinal bacterial structure. This study provides novel guidance to develop novel food or dietary supplements to improve HE diseases due to the potential beneficial effect of COS on gut-liver axis.

Selection of Non-Saccharomyces Wine Yeasts for the Production of Leavened Doughs

Background: Non-conventional yeasts (NCY) (i.e., non-Saccharomyces) may be used as alternative starters to promote biodiversity and quality of fermented foods and beverages (e.g., wine, beer, bakery products). Methods: A total of 32 wine-associated yeasts (Campania region, Italy) were genetically identified and screened for decarboxylase activity and leavening ability. The best selected strains were used to study the leavening kinetics in model doughs (MDs). A commercial strain of Saccharomyces cerevisiae was used as the control. The volatile organic profiles of the inoculated MDs were analyzed by solid phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS). Results: Most of strains belonged to the NCY species Hanseniaspora uvarum, Metschnikowia pulcherrima, Pichia kudriavzevii, Torulaspora delbruekii, and Zygotorulaspora florentina, while a few strains were S. cerevisiae. Most strains of H. uvarum lacked decarboxylase activity and showed a high leaving activity after 24 h of incubation that was comparable to the S. cerevisiae strains. The selected H. uvarum strains generated a different flavor profile of the doughs compared to the S. cerevisiae strains. In particular, NCY reduced the fraction of aldehydes that were potentially involved in oxidative phenomena. Conclusions: The use of NCY could be advantageous in the bakery industry, as they can provide greater diversity than S. cerevisiae-based products, and may be useful in reducing and avoiding yeast intolerance.

Recent developments in the biology and biotechnological applications of halotolerant yeasts

Natural hypersaline environments are inhabited by an abundance of prokaryotic and eukaryotic microorganisms capable of thriving under extreme saline conditions. Yeasts represent a substantial fraction of halotolerant eukaryotic microbiomes and are frequently isolated as food contaminants and from solar salterns. During the last years, a handful of new species has been discovered in moderate saline environments, including estuarine and deep-sea waters. Although Saccharomyces cerevisiae is considered the primary osmoadaptation model system for studies of hyperosmotic stress conditions, our increasing understanding of the physiology and molecular biology of halotolerant yeasts provides new insights into their distinct metabolic traits and provides novel and innovative opportunities for genome mining of biotechnologically relevant genes. Yeast species such as Debaryomyces hansenii, Zygosaccharomyces rouxii, Hortaea werneckii and Wallemia ichthyophaga show unique properties, which make them attractive for biotechnological applications. Select halotolerant yeasts are used in food processing and contribute to aromas and taste, while certain gene clusters are used in second generation biofuel production. Finally, both pharmaceutical and chemical industries benefit from applications of halotolerant yeasts as biocatalysts. This comprehensive review summarizes the most recent findings related to the biology of industrially-important halotolerant yeasts and provides a detailed and up-to-date description of modern halotolerant yeast-based biotechnological applications.

Quantification of Biogenic Amines in 35 Korean Cottage Industry Traditional Gochujang (Fermented Red Pepper Paste) Products

Traditional gochujang is well known for its distinguished flavor and taste. However, the safety of cottage industry gochujang products is uncertain, particularly, in terms of biogenic amine (BA) content which is not yet documented. The present study aimed to determine the level of BAs present in 35 traditional gochujang products nationwide. All gochujang products had considerable amounts of total BAs ranging from 52.95 mg/kg to 176.24 mg/kg. Individually, histamine and tyramine were either not detected or detected up to 16.94 mg/kg and 2.15–52.34 mg/kg, respectively. In all the tested gochujang products, putrescine, spermidine, and spermine were detected in the range of 7.60–56.72 mg/kg, 14.96–36.93 mg/kg, and 4.68–16.31 mg/kg, respectively. A total of 22 and 19 gochujang products had less than 1 mg/kg of cadaverine and histamine, respectively. The findings indicate that all the gochujang products tested herein had BA levels below the suggested toxicity limits recommended by the various regulatory authorities, which reveal that they are safe for human consumption.

Considering histamine in functional gastrointestinal disorders

In westernized countries, adverse reactions to ingested foods are reported to affect up to 20% of the population. Functional, nonspecific, non-allergic gastrointestinal complaints are mainly due to the intolerance/malabsorption of carbohydrates (lactose and fructose), proteins (gluten), and biogenic amines (histamine). Food intolerance/malabsorption is defined by one or several of the above mentioned food components not being degraded and/or absorbed properly within the gastrointestinal tract. Food intolerance/malabsorption causes variable, functional, nonspecific, non-allergic gastrointestinal and extra-intestinal complaints, and a detailed diagnostic workup for all possible etiologic factors in individual patients is essential. Usually, evaluation for histamine intolerance is not included in differential diagnoses of patients with functional, nonspecific, non-allergic gastrointestinal complaints. A targeted dietary intervention for single or possibly combined intolerance/malabsorption is required. In this article, we review currently discussed differential diagnoses and available tests for intolerance/malabsorption. Accordingly, we aim to outline why including histamine and, histamine intolerance, should be considered in differential diagnoses of patients with functional, nonspecific, non-allergic gastrointestinal complaints.

Characterizing the effect of packaging material and storage temperature on the flavor profiles and quality of soy sauce

The effect of packaging material and storage temperature on two types of soy sauce was investigated. Ethanol content decreased significantly in all tested samples after storage (P < 0.05). While the changes of physicochemical properties and CIELAB color space indexes varied with soy sauce types, packaging materials and storage temperatures. The changes of volatile profiles after storage indicated that storage temperature was a key factor resulting in flavor scalping. It also suggested that there was no significant difference of flavor compounds sorption between glass bottle and polyethylene terephthalate bottle. The abundances of acids and alcohols increased after stored at ambient temperature (AT) and low temperature (LT) for 90 days, but phenols decreased. The effect of the packaging material, raw soy sauce type and storage temperature resulted in changing the intensities of fruity, caramel-like, mushroom-like note as well as smoky note. For the inoculated soy sauces, 1-octen-3-ol, ethyl hexanoate and ethyl octanoate in the samples were dominant in samples stored at AT, while the samples stored at LT were characterized by multiple components according to the results of principal components analysis. These results were benefit for understanding the main factors affecting the flavor profiles and quality of soy sauce during storage, as well as optimizing the storage condition.

Dynamic Changes in Biogenic Amine Content in the Traditional Brewing Process of Soy Sauce

A high concentration of biogenic amines have been reported to be hazardous for human health. This article is an analytical report on one lot to identify the changes of biogenic amines in each period of soy sauce brewing and clarify the key control point for biogenic amine production. The content of putrescine, cadaverine, spermidine, spermine, tryptamine, phenylethylamine, histamine, serotonin, tyramine, and agmatine was detected in the koji-making and fermenting process. The content of putrescine increased from 27.11 ± 1.05 to 185.86 ± 1.18 mg/kg in the koji-making process, indicating that putrescine is the main biogenic amine produced by microbes in this period. The content of tryptamine increased to the highest value of 581.77 ± 36.38 mg/L on day 24 of the fermenting process and then decreased rapidly to 81.98 ± 0.20 mg/L at the end (day 122). In addition, histamine and tyramine reached the highest values (486.91 ± 24.67 and 180.84 ± 2.32 mg/L, respectively) after 52 days of fermentation, followed by a decrease to 287.24 ± 15.00 and 144.67 ± 3.61 mg/L, respectively, at the end of the fermenting process. The samples were further characterized by the analysis of other indices, including the content of water, salt, soluble saltless solids, crude fat, total acid, amino acid nitrogen, total nitrogen, and ammonium salt. The content of soluble saltless solids decreased from 9.28 ± 0.16 to 5.30 ± 1.40 g/100 g during the first 38 days of fermentation, followed by an increase to 14.68 ± 1.12 g/100 g during the last 84 days. The content of total acid, crude fat, amino acid nitrogen, total nitrogen, and ammonium salt all increased rapidly in the early stage of the fermenting process and then slowed down.

Comparison of Biogenic Amines in Chinese Commercial Soy Sauces

Soy sauce contains a series of biogenic amines (BAs) which is a kind of bioactive organics relating to food quality and safety. High concentration of BAs may lead to remarkable physiological and toxicological influences on human bodies, including hypotension, dizziness, and headaches. Here, we systematically compared the levels of ten main BAs among 53 Chinese commercial soy sauces using an improved high-performance liquid chromatography (HPLC) method. The results showed that the brands and production regions were both important factors accounting for the BAs’ content. The contents of Cad, Spm, Try, Phe, His, and Tyr in dark soy sauces were higher than those in light soy sauces. His and Phe in dark soy sauces were 3.7 and 1.84 times higher than in light samples, respectively. Besides, it was surprising that the content of BAs in soy sauces hugely varied from place to place. This work comprehensively compared the content of BAs in soy sauces, showing the relation between soy sauce processes and BAs, offering abundant information for further research on BAs control.

Draft genome sequence of Candida versatilis and osmotolerance analysis in soy sauce fermentation

BACKGROUND

The salt-tolerant yeast strain Candida versatilis is usually added to high-salt, liquid-state soy sauce fermentation. The genome of C. versatilis was sequenced in our previous study but the reason for its high-osmolarity ability was not clear.

RESULTS

The 9.7 Mbp genome of C. versatilis contained 4711 CDS. Candida versatilis was the closest to another yeast, Zygosaccharomyces rouxii, added to soy sauce fermentation. The protein sequence of the whole genome was divided into 4338 groups, accounting for 92.1% of all the predicted protein of C. versatilis using OrthoMCL. Mitogen-activated protein kinase (MAPK) signal pathways, including high osmolarity and cell integrity, were predicted and proved by investigating the expression changes of the key genes CvHOG1, CvGPD1, and CvFPS1 in a high osmotic environment and by testing the variations of intracellular glycerol and extracellular glycerol.

CONCLUSION

Candida versatilis exhibited strong osmotolerance because it could synthesize intracellular glycerol and absorb glycerol from the environment cooperated with the shut down of glycerol efflux channel in membrane. © 2018 Society of Chemical Industry.

Biogenic Amine Production by Lactic Acid Bacteria: A Review

Lactic acid bacteria (LAB) are considered as the main biogenic amine (BA) producers in fermented foods. These compounds derive from amino acid decarboxylation through microbial activities and can cause toxic effects on humans, with symptoms (headache, heart palpitations, vomiting, diarrhea) depending also on individual sensitivity. Many studies have focused on the aminobiogenic potential of LAB associated with fermented foods, taking into consideration the conditions affecting BA accumulation and enzymes/genes involved in the biosynthetic mechanisms. This review describes in detail the different LAB (used as starter cultures to improve technological and sensorial properties, as well as those naturally occurring during ripening or in spontaneous fermentations) able to produce BAs in model or in real systems. The groups considered were enterococci, lactobacilli, streptococci, lactococci, pediococci, oenococci and, as minor producers, LAB belonging to Leuconostoc and Weissella genus. A deeper knowledge of this issue is important because decarboxylase activities are often related to strains rather than to species or genera. Moreover, this information can help to improve the selection of strains for further applications as starter or bioprotective cultures, in order to obtain high quality foods with reduced BA content.

Development of Safe and Flavor-Rich Doenjang (Korean Fermented Soybean Paste) Using Autochthonous Mixed Starters at the Pilot Plant Scale

Doenjang (Korean fermented soybean paste) with an improved flavor and safety was prepared by the simultaneous fermentation of autochthonous mixed starters at the pilot plan scale. First, whole soybean meju was fermented by coculturing safety-verified starters Aspergillus oryzae MJS14 and Bacillus amyloliquefaciens zip6 or Bacillus subtilis D119C. These fermented whole soybean meju were aged in a brine solution after the additional inoculation of Tetragenococcus halophilus 7BDE22 and Zygosaccharomyces rouxii SMY045 to yield doenjang. Four doenjang batches prepared using a combination of mold, bacilli, lactic acid bacteria, and yeast starters were free of safety issues and had the general properties of traditional doenjang, a rich flavor and taste. All doenjang batches received a high consumer acceptability score, especially the ABsT and ABsTZ batches. This study suggests that flavor-rich doenjang similar to traditional doenjang can be manufactured safely and reproducibly in industry by mimicking the simultaneous fermentation of autochthonous mixed starters as in traditional doenjang fermentation.

PRACTICAL APPLICATION

The development of a pilot plant process for doenjang fermentation using safety-verified autochthonous mixed starter will facilitate the manufacture of flavor-rich doenjang similar to traditional doenjang safely and reproducibly in industry.

Non-celiac gluten sensitivity: people without celiac disease avoiding gluten-is it due to histamine intolerance?

INTRODUCTION

Food intolerance/malabsorption is caused by food ingredients, carbohydrates (mainly lactose and fructose), proteins (gluten), and biogenic amines (histamine) which cause nonspecific gastrointestinal and extra-intestinal symptoms. Here we focus on possible etiologic factors of intolerance/malabsorption especially in people with non-celiac gluten sensitivity (NCGS) or the so-called people without celiac disease avoiding gluten (PWCDAG) and histamine intolerance.

METHODS

Recognizing the recently described symptoms of NCGS (PWCDAG) we review correlations and parallels to histamine intolerance (HIT).

RESULTS

We show that intestinal and extra-intestinal NCGS (PWCDAG) symptoms are very similar to those which can be found in histamine intolerance.

CONCLUSIONS

After a detailed diagnostic workup for all possible etiologic factors in every patient, a targeted dietary intervention for single or possibly combined intolerance/malabsorption might be more effective than a short-term diet low in fermentable oligo-, di- and monosaccharides and polyols (FODMAP) or the untargeted uncritical use of gluten-free diets.

Comparative study on fermentation performance in the genome shuffled Candida versatilis and wild-type salt tolerant yeast strain

BACKGROUND

The fermentation performance of a genome-shuffled strain of Candida versatilis S3-5, isolated for improved tolerance to salt, and wild-type (WT) strain were analysed. The fermentation parameters, such as growth, reducing sugar, ethanol, organic acids and volatile compounds, were detected during soy sauce fermentation process.

RESULTS

The results showed that ethanol produced by the genome shuffled strain S3-5 was increasing at a faster rate and to a greater extent than WT. At the end of the fermentation, malic acid, citric acid and succinic acid formed in tricarboxylic acid cycle after S3-5 treatment elevated by 39.20%, 6.85% and 17.09% compared to WT, respectively. Moreover, flavour compounds such as phenethyl acetate, ethyl vanillate, ethyl acetate, isoamyl acetate, ethyl myristate, ethyl pentadecanoate, ethyl palmitate and phenylacetaldehyde produced by S3-5 were 2.26, 2.12, 2.87, 34.41, 6.32, 13.64, 2.23 and 78.85 times as compared to WT.

CONCLUSIONS

S3-5 exhibited enhanced metabolic ability as compared to the wild-type strain, improved conversion of sugars to ethanol, metabolism of organic acid and formation of volatile compounds, especially esters, Moreover, S3-5 might be an ester-flavour type salt-tolerant yeast. © 2016 Society of Chemical Industry.

Technological Factors Affecting Biogenic Amine Content in Foods: A Review

Biogenic amines (BAs) are molecules, which can be present in foods and, due to their toxicity, can cause adverse effects on the consumers. BAs are generally produced by microbial decarboxylation of amino acids in food products. The most significant BAs occurring in foods are histamine, tyramine, putrescine, cadaverine, tryptamine, 2-phenylethylamine, spermine, spermidine, and agmatine. The importance of preventing the excessive accumulation of BAs in foods is related to their impact on human health and food quality. Quality criteria in connection with the presence of BAs in food and food products are necessary from a toxicological point of view. This is particularly important in fermented foods in which the massive microbial proliferation required for obtaining specific products is often relater with BAs accumulation. In this review, up-to-date information and recent discoveries about technological factors affecting BA content in foods are reviewed. Specifically, BA forming-microorganism and decarboxylation activity, genetic and metabolic organization of decarboxylases, risk associated to BAs (histamine, tyramine toxicity, and other BAs), environmental factors influencing BA formation (temperature, salt concentration, and pH). In addition, the technological factors for controlling BA production (use of starter culture, technological additives, effects of packaging, other non-thermal treatments, metabolizing BA by microorganisms, effects of pressure treatments on BA formation and antimicrobial substances) are addressed.

Chromohalobacter is a Causing Agent for the Production of Organic Acids and Putrescine during Fermentation of Ganjang, a Korean Traditional Soy Sauce

Ganjang, a Korean traditional fermented soy sauce, is prepared by soaking doenjang-meju (fermented soybeans) in approximately 20% (w/v) solar salt solution. The metabolites and bacterial communities during ganjang fermentation were simultaneously investigated to gain a better understanding of the roles of the microbial population. The bacterial community analysis based on denaturing gradient gel electrophoresis of 16S rRNA gene sequences showed that initially, the genus Cobetia was predominant (0 to 10 d), followed by Bacillus (5 to 74 d), and eventually, Chromohalobacter became predominant until the end of the fermentation process (74 to 374 d). Metabolite analysis using (1)H-NMR showed that carbon compounds, such as fructose, galactose, glucose, and glycerol, probably released from doenjang-meju, increased rapidly during the early fermentation period (0 to 42 d). After removal of doenjang-meju from the ganjang solution (42 d), the initial carbon compounds remained nearly constant without the increase of fermentation products. At this point, Bacillus species, which probably originated from doenjang-meju, were predominant, suggesting that Bacillus is not mainly responsible for ganjang fermentation. Fermentation products including acetate, lactate, α-aminobutyrate, γ-aminobutyrate, and putrescine increased quickly with the rapid decrease of the initial carbon compounds, while Chromohalobacter, probably derived from the solar salts, was predominant. Multivariate redundancy analysis indicated that the Chromohalobacter population was closely correlated with the production of the organic acids and putrescine during the ganjang fermentation. These results may suggest that Chromohalobacter is a causing agent responsible for the production of organic acids and putrescine during ganjang fermentation and that the solar salts, not doenjang-meju, is an important microbial source for ganjang fermentation.

Synthesis of α-amino acidato derivatives of niobium and tantalum pentahalides and their conversion into iminium salts

Dinuclear complexes of formula Nb2Cl9[O2CCH(R)NR'R″2-κO,κO] (R = CH2CHMe2, R' = R″ = H, 1a; R = CH2Ph, R' = R″ = H, 1b; R = CH2CH2SCH3, R' = R″ = H, 1c; R = R' = H, R″ = Me, 1d; R = CH2Ph, R' = R″ = Me, 1e; Nb2Cl9[O2C⌈CH(CH2)3NH⌉], 1f) were prepared by allowing NbCl5 to react in dichloromethane with the appropriate α-amino acid in 1:2 amino acid/Nb molar ratio. The 1:1 reactions between MX5 (M = Nb, Ta; X = Cl, Br) and a series of α-amino acids resulted in the formation of the iminium salts [(R)CH═NR'R″2][MX6] (R = CH2Ph, R' = R″ = Me: M = Nb, X = Cl, 2a; M = Nb, X = Br, 2b; M = Ta, X = Cl, 2c; M = Ta, X = Br, 2d; R = CH2Ph, R' = R″ = H, M = Nb: X = Cl, 3a; X = Br, 3b; R = CH2CHMe2, R' = R″ = H, M = Nb, X = Cl, 4; R = R' = H, R″ = Me, M = Nb, X = Cl, 5). The formate/amino acidate derivative NbCl3(O2CH)[O2CCH(CH2Ph)NMe2], 6, was isolated and identified as coproduct of the 1:1 reaction between NbCl5 and N,N-dimethyl-l-phenylalanine, leading to 2a. All of the compounds were characterized by analytical and spectroscopic methods and by X-ray diffractometry in the cases of 2a, 2b, and 2d. Moreover, density functional theory studies were carried out to shed light on mechanistic and structural aspects.