A β-glucosidase from Oenococcus oeni ATCC BAA-1163 with potential for aroma release in wine: Cloning and expression in E. coli

Characterization and stabilization of GluLm and its application to deglycosylate dietary flavonoids and lignans

This study describes the characterization of the recombinant GH3 aryl-β-glucosidase "GluLm" from Limosilactobacillus mucosae INIA P508, followed by its immobilization on an agarose support with the aim of developing an efficient application to increase the availability and concentration of flavonoid and lignan aglycones in a vegetal beverage. In previous studies, heterologous GluLm-producing strains demonstrated a great capacity to deglycosylate flavonoids. Nevertheless, the physicochemical properties and substrate spectrum of the enzyme remained unknown up to now. A high production of purified GluLm was achieved (14 mg L-1). GluLm exhibited optimal activity at broad ranges of pH (5.0-8.0) and temperature (25-60°C), as well as high affinity (Km of 0.10 mmol L-1) and specific constant (86554.0 mmol L-1 s-1) against p-nitrophenyl-β-D-glucopyranoside. Similar to other GH3 β-glucosidases described in lactic acid bacteria, GluLm exhibited β-xylosidase, β-galactosidase, and β-fucosidase activities. However, this study has revealed for the first time that a GH3 β-glucosidase is capable to hydrolyze different families of glycosylated phenolics such as flavonoids and secoiridoids. Although it exhibited low thermal stability, immobilization of GluLm improved its thermostability and allowed the development of a beverage based on soybeans and flaxseed extract with high concentration of bioactive isoflavone (daidzein, genistein), lignan (secoisolariciresinol, pinoresinol, and matairesinol), and other flavonoid aglycones. KEY POINTS: • Limosilactobacillus mucosae INIA P508 GluLm was purified and biochemically characterized • Immobilized GluLm efficiently deglycosylated flavonoids and lignans from a vegetal beverage • A viable application to produce vegetal beverages with a high content of aglycones is described.

Effect of Yogurt Addition on the Stability of Anthocyanin during Cold Storage of Strawberry, Raspberry, and Blueberry Smoothies

The addition of yogurt to fruit smoothies enhances their nutritional value by introducing components not naturally found in fruit products. However, the addition of fermented products can affect the stability of fruit bioactive components in fruits, such as anthocyanins. This study aimed to evaluate the effect of varying yogurt additions (0, 10, 20, and 30%) on the stability of anthocyanins during a 4-week refrigerated storage period. The smoothies were obtained from purees of strawberry, raspberry, and blueberry, combined with apple juice and apple puree. In addition, to elucidate the causes of the observed changes in the smoothies, model studies were conducted using purified anthocyanin extracts obtained from the analyzed fruits. We assessed the effects of pH, hydrogen peroxide concentration, and the addition of cell-free extracts from Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus on changes in anthocyanin content during storage. We found that adding yogurt led to a decrease in anthocyanin stability during the 4-week cold storage period. Specifically, a 30% yogurt addition decreased anthocyanin stability in all tested beverages, while a 20% yogurt addition impacted the strawberry and raspberry smoothies. The degree to which yogurt affected anthocyanin stability was dependent on the source of the raw material. The most notable impact was observed in strawberry smoothies and the least in blueberry smoothies. The variability could be attributed to differences in anthocyanin profiles among the fruits, the chemical composition of the beverages, and the observed difference in the survival rates of lactic acid bacteria. Model studies showed that during the storage of anthocyanin extracts, the addition of hydrogen peroxide and cell-free extract had a significant effect, whereas pH within the examined range (3.0-4.5) did not affect anthocyanin stability.

Characterisation of recombinant GH 3 β-glucosidase from β-glucan producing Levilactobacillus brevis TMW 1.2112

Levilactobacillus (L.) brevis TMW 1.2112 is an isolate from wheat beer that produces O2-substituted (1,3)-β-D-glucan, a capsular exopolysaccharide (EPS) from activated sugar nucleotide precursors by use of a glycosyltransferase. Within the genome sequence of L. brevis TMW 1.2112 enzymes of the glycoside hydrolases families were identified. Glycoside hydrolases (GH) are carbohydrate-active enzymes, able to hydrolyse glycosidic bonds. The enzyme β-glucosidase BglB (AZI09_02170) was heterologous expressed in Escherichia coli BL21. BglB has a monomeric structure of 83.5 kDa and is a member of the glycoside hydrolase family 3 (GH 3) which strongly favoured substrates with β-glycosidic bonds. Km was 0.22 mM for pNP β-D-glucopyranoside demonstrating a high affinity of the recombinant enzyme for the substrate. Enzymes able to degrade the (1,3)-β-D-glucan of L. brevis TMW 1.2112 have not yet been described. However, BglB showed only a low hydrolytic activity towards the EPS, which was measured by means of the D-glucose releases. Besides, characterised GH 3 β-glucosidases from various lactic acid bacteria (LAB) were phylogenetically analysed to identify connections in terms of enzymatic activity and β-glucan formation. This revealed that the family of GH 3 β-glucosidases of LABs comprises most likely exo-active enzymes which are not directly associated with the ability of these LAB to produce EPS.

Localization, purification, and characterization of a novel β-glucosidase from Hanseniaspora uvarum Yun268

β-Glucosidase is a key enzyme that hydrolyzes nonvolatile glycosylated precursors of aroma compounds and enhances the organoleptic quality of wines. In this study, a novel β-glucosidase from Hanseniaspora uvarum Yun268 was localized, purified, and characterized. Results indicated that β-glucosidase activity was mainly distributed within the cells. After purification via ammonium sulfate precipitation combined with chromatography, β-glucosidase specific activity increased 8.36 times, and the activity recovery was 56.90%. The enzyme had a molecular mass of 74.22 kDa. It has a Michaelis constant (K_m ) of 0.65 mmol/L, and a maximum velocity (V_max ) of 5.1 nmol/min under optimum conditions; and K_m of 0.94 mmol/L, and V_max of 2.8 nmol/min under typical winemaking conditions. It exhibited the highest activity at 50°C and pH 5.0 and was stable at a temperature range of 20-80°C and pH range of 3.0-8.0. The enzyme has good tolerance to Fe³⁺ , especially maintaining 93.68% of its activity with 10 mmol/L of Fe³⁺ . Ethanol (<20%) and glucose (<150 g/L) inhibited its activity only slightly. Therefore, β-glucosidase from H. uvarum Yun268 has excellent biochemical properties and a good application potential in winemaking. PRACTICAL APPLICATION: Winemaking is a biotechnological process in which exogenous β-glucosidase is used to overcome the deficiency of endogenous β-glucosidase activity in grapes. By localizing, purifying, and characterizing of β-glucosidase from Hanseniaspora uvarum Yun268, it is expected to reveal its physical and chemical characteristics to evaluate its oenological properties in winemaking. The results may provide the basis for promoting the release of varietal aroma and improving wine sensory quality in the wine industry.

Lactic Acid Bacteria in Wine: Technological Advances and Evaluation of Their Functional Role

Currently, the main role of Lactic Acid Bacteria (LAB) in wine is to conduct the malolactic fermentation (MLF). This process can increase wine aroma and mouthfeel, improve microbial stability and reduce the acidity of wine. A growing number of studies support the appreciation that LAB can also significantly, positively and negatively, contribute to the sensorial profile of wine through many different enzymatic pathways. This is achieved either through the synthesis of compounds such as diacetyl and esters or by liberating bound aroma compounds such as glycoside-bound primary aromas and volatile thiols which are odorless in their bound form. LAB can also liberate hydroxycinnamic acids from their tartaric esters and have the potential to break down anthocyanin glucosides, thus impacting wine color. LAB can also produce enzymes with the potential to help in the winemaking process and contribute to stabilizing the final product. For example, LAB exhibit peptidolytic and proteolytic activity that could break down the proteins causing wine haze, potentially reducing the need for bentonite addition. Other potential contributions include pectinolytic activity, which could aid juice clarification and the ability to break down acetaldehyde, even when bound to SO2, reducing the need for SO2 additions during winemaking. Considering all these findings, this review summarizes the novel enzymatic activities of LAB that positively or negatively affect the quality of wine. Inoculation strategies, LAB improvement strategies, their potential to be used as targeted additions, and technological advances involving their use in wine are highlighted along with suggestions for future research.

Assessment of β-D-glucosidase activity and bgl gene expression of Oenococcus oeni SD-2a

Glycosidases enhance flavor during wine-making by mediating the enzymatic release of aroma molecules. In order to better understand the aroma enhancement potential of Oenococcus oeni SD-2a, β-D-glucosidase (βG) activities in the culture supernatant, whole cells, and disrupted cell lysate were assessed at mid log, late log and stationary growth phase. The enzymatic activity was also compared further from cell cultures with 5 different carbon sources (glucose, cellobiose, arbutin, glucose and cellobiose, glucose and arbutin) at late log phase. Correspondingly, expression levels of 3 bgl genes, OEOE-0224, OEOE-1210, and OEOE-1569 were investigated from cell cultures of the 3 growth phases, and the 5 cell cultures with different carbon sources. Finally, the volatile aroma compounds released by O. oeni SD-2a in synthetic wines with natural glycosides were evaluated by GC-MS. Results showed βG of O. oeni SD-2a was not extracellular enzyme, and the location of it didn’t change with the change of growth phase and carbon source studied. βG activities in the whole cells and disrupted cell lysate were similar and constant at the 3 growth phases. As for the carbon sources, βG activities of whole cells and disrupted lysate were positively affected by cellobiose. While arbutin displayed positive and negative effect on βG activity of whole cells and disrupted lysate, respectively. It is probably that bgl genes OEOE-0224 and OEOE-1210 were related to βG activity of SD-2a whole cells, while OEOE-1569 was responsible for βG activity of disrupted lysate. More kinds of volatile compounds and higher total concentration were released by SD-2a in synthetic wine compared with control. Thus, SD-2a showed a great potential for flavor enhancement under wine-like conditions. This study provides more information for further study of βG activity from O. oeni SD-2a.

Homology analysis of 35 β-glucosidases in Oenococcus oeni and biochemical characterization of a novel β-glucosidase BGL0224

β-Glucosidases play an important role in food industry. Oenococcus oeni are typical lactic acid bacteria that initiate malolactic fermentation of wines. 35 β-glucosidases from O. oeni were selected and their conserved domains and evolutionary relationships were further explored in this study. The homology analysis results indicated that 35 β-glucosidases were basically derived from GH1 and GH3 family. A novel β-glucosidase was successfully expressed and characterized. The recombinant protein, referred to as BGL0224, consisted of a total 480 amino acids with an apparent molecular weight of 55.15 kDa and was classified as GH1 family. It achieved the highest activity at pH 5.0 and 50 °C. The activity and stability were significantly increased when 12% ethanol was supplemented to the enzyme. Using p-NPG as substrate, the K_m, V_max and K_cat of BGL0224 were 0.34 mM, 382.81 U/mg and 351.88 s^-1, respectively. In all, BGL0224 has good application prospects in food industry.

Taxogenomic assessment and genomic characterisation of Weissella cibaria strain 92 able to metabolise oligosaccharides derived from dietary fibres

The importance of the gut microbiota in human health has led to an increased interest to study probiotic bacteria. Fermented food is a source of already established probiotics, but it also offers an opportunity to discover new taxa. Four strains of Weissella sp. isolated from Indian fermented food have been genome sequenced and classified into the species W. cibaria based on whole-genome phylogeny. The genome of W. cibaria strain 92, known to utilise xylooligosaccharides and produce lactate and acetate, was analysed to identify genes for oligosaccharide utilisation. Clusters including genes involved in transportation, hydrolysis and metabolism of xylooligosaccharides, arabinooligosaccharides and β-glucosides were identified. Growth on arabinobiose and laminaribiose was detected. A 6-phospho-β-glucosidase clustered with a phosphotransferase system was found upregulated during growth on laminaribiose, indicating a mechanism for laminaribiose utilisation. The genome of W. cibaria strain 92 harbours genes for utilising the phosphoketolase pathway for the production of both acetate and lactate from pentose and hexose sugars but lacks two genes necessary for utilising the pentose phosphate pathway. The ability of W. cibaria strain 92 to utilise several types of oligosaccharides derived from dietary fibres, and produce lactate and acetate makes it interesting as a probiotic candidate for further evaluation.

Modified mycotoxins: An updated review on their formation, detection, occurrence, and toxic effects

Modified mycotoxins are metabolites that normally remain undetected during the testing for parent mycotoxin. These modified forms of mycotoxins can be produced by fungi or generated as part of the defense mechanism of the infected plant. In some cases, they are formed during food processing. The various processing steps greatly affect mycotoxin levels present in the final product (free and modified), although the results are still controversial regarding the increase or reduction of these levels, being strongly related to the type of process and the composition of the food in question. Evidence exists that some modified mycotoxins can be converted into the parent mycotoxin during digestion in humans and animals, potentially leading to adverse health effects. Some of these formed compounds can be even more toxic, in case they have higher bioaccessibility and bioavailability than the parent mycotoxin. The modified mycotoxins can occur simultaneously with the free mycotoxin, and, in some cases, the concentration of modified mycotoxins may exceed the level of free mycotoxin in processed foods. Even though toxicological data are scarce, the possibility of modified mycotoxin conversion to its free form may result in a potential risk to human and animal health. This review aims to update information on the formation, detection, occurrence, and toxic effects caused by modified mycotoxin.

Aroma Glycosides in Grapes and Wine

The major aroma components in grapes and wine include free volatile compounds and glycosidic nonvolatile compounds. The latter group of compounds is more than 10 times abundant of the former, and constitutes a big aroma reserve in grapes and wine. This review summarizes the research results obtained recently for the identification of aroma glycosides in grapes and wine, including grape glycoside structures, differences in aroma glycosides among grape varieties, hydrolysis mechanisms, and the factors that influence them. It also presents the analytical techniques used to identify the glycosidic aroma precursors. The operational strategies, challenges, and improvements of each step encountered in the analysis of glycosidic aroma precursors are described. This review intends to provide a convenient reference for researchers interested in the methods used for the determination of the aroma glucosides composition and the recognition of their chemical structures.

Linking wine lactic acid bacteria diversity with wine aroma and flavour

In the last two decades knowledge on lactic acid bacteria (LAB) associated with wine has increased considerably. Investigations on genetic and biochemistry of species involved in malolactic fermentation, such as Oenococcus oeni and of Lactobacillus have enabled a better understand of their role in aroma modification and microbial stability of wine. In particular, the use of molecular techniques has provided evidence on the high diversity at species and strain level, thus improving the knowledge on wine LAB taxonomy and ecology. These tools demonstrated to also be useful to detect strains with potential desirable or undesirable traits for winemaking purposes. At the same time, advances on the enzymatic properties of wine LAB responsible for the development of wine aroma molecules have been undertaken. Interestingly, it has highlighted the high intraspecific variability of enzymatic activities such as glucosidase, esterase, proteases and those related to citrate metabolism within the wine LAB species. This genetic and biochemistry diversity that characterizes wine LAB populations can generate a wide spectrum of wine sensory outcomes. This review examines some of these interesting aspects as a way to elucidate the link between LAB diversity with wine aroma and flavour. In particular, the correlation between inter- and intra-species diversity and bacterial metabolic traits that affect the organoleptic properties of wines is highlighted with emphasis on the importance of enzymatic potential of bacteria for the selection of starter cultures to control MLF and to enhance wine aroma.

Identification and Localization of β-D-Glucosidase from Two Typical Oenococcus oeni Strains

β-D-glucosidase (βG) gene from Oenococcus oeni SD-2a and 31MBR was cloned, sequenced and analyzed, also intracellular βG of the two strains was further localized. The results showed that βG gene of the two strains was in high homology (> 99%) to reported βG gene, con-firming both strains possess βG activity at the molecular level. Intracellular βG of SD-2a is a mainly soluble protein, existing mostly in the cytoplasm and to some extent in the periplasm. While for 31MBR, intracellular βG is mainly insoluble protein existing in the cytoplasmic membrane. This study provides basic information for further study of the metabolic mechanism of βG from O. oeni SD-2a and 31MBR.

Optimization of a heat-tolerant β-glucosidase production by Bacillus sp. ZJ1308 and its purification and characterization

Response surface methodology was used to optimize the medium composition to improve the production of the heat-tolerant β-glucosidase from Bacillus sp. ZJ1308. Three significant factors were found to be corn cob, beef extract, and MnSO4 ·H2 O. The final medium compositions optimized were corn cob (51.8 g/L), beef extract (23.8 g/L), salicin (0.5 g/L), MnSO4 ·H2 O (0.363 g/L), MgSO4 ·7H2 O (0.4 g/L), and NaCl (5 g/L). Under the optimal conditions, the activity of β-glucosidase was up to 4.71 U/mL. β-Glucosidase was purified to homogeneity with a recovery rate of 5% and a specific activity of 110.47 U/mg. The optimal pH and temperature were 7.0 and 60 °C, respectively. β-Glucosidase was stable within a pH range of 6.0-8.0 and showed an extremely high thermostability at 80 and 90 °C, retaining 56% and 38% of its maximal activity, respectively. Ni(2+) and Ba(2+) heavily inhibited the β-glucosidase activity. The purified β-glucosidase showed a high substrate specificity. The kinetic parameters revealed that it had a high catalytic efficiency toward the substrate p-nitrophenyl-β-d-glucopyranoside (Kcat /Km = 700). It also showed a high catalytic activity toward the natural substrate salicin. This study provides a new insight into the future development and use of β-glucosidase from Bacillus sp. ZJ1308.

A Versatile Family 3 Glycoside Hydrolase from Bifidobacterium adolescentis Hydrolyzes β-Glucosides of the Fusarium Mycotoxins Deoxynivalenol, Nivalenol, and HT-2 Toxin in Cereal Matrices

Glycosylation plays a central role in plant defense against xenobiotics, including mycotoxins. Glucoconjugates of Fusarium toxins, such as deoxynivalenol-3-O-β-d-glucoside (DON-3G), often cooccur with their parental toxins in cereal-based food and feed. To date, only limited information exists on the occurrence of glucosylated mycotoxins and their toxicological relevance. Due to a lack of analytical standards and the requirement of high-end analytical instrumentation for their direct determination, hydrolytic cleavage of β-glucosides followed by analysis of the released parental toxins has been proposed as an indirect determination approach. This study compares the abilities of several fungal and recombinant bacterial β-glucosidases to hydrolyze the model analyte DON-3G. Furthermore, substrate specificities of two fungal and two bacterial (Lactobacillus brevis and Bifidobacterium adolescentis) glycoside hydrolase family 3 β-glucosidases were evaluated on a broader range of substrates. The purified recombinant enzyme from B. adolescentis (BaBgl) displayed high flexibility in substrate specificity and exerted the highest hydrolytic activity toward 3-O-β-d-glucosides of the trichothecenes deoxynivalenol (DON), nivalenol, and HT-2 toxin. A Km of 5.4 mM and a Vmax of 16 μmol min(-1) mg(-1) were determined with DON-3G. Due to low product inhibition (DON and glucose) and sufficient activity in several extracts of cereal matrices, this enzyme has the potential to be used for indirect analyses of trichothecene-β-glucosides in cereal samples.

Zearalenone-16-O-glucoside: a new masked mycotoxin

This paper reports the identification of a barley UDP-glucosyltransferase, HvUGT14077, which is able to convert the estrogenic Fusarium mycotoxin zearalenone into a near-equimolar mixture of the known masked mycotoxin zearalenone-14-O-β-glucoside and a new glucose conjugate, zearalenone-16-O-β-glucoside. Biocatalytical production using engineered yeast expressing the HvUGT14077 gene allowed structural elucidation of this compound. The purified zearalenone-16-O-β-glucoside was used as an analytical calibrant in zearalenone metabolization experiments. This study confirmed the formation of this new masked mycotoxin in barley seedlings as well as in wheat and Brachypodium distachyon cell suspension cultures. In barley roots, up to 18-fold higher levels of zearalenone-16-O-β-glucoside compared to the known zearalenone-14-O-β-glucoside were found. Incubation of zearalenone-16-O-β-glucoside with human fecal slurry showed that this conjugate can also be hydrolyzed rapidly by intestinal bacteria, converting the glucoside back to the parental mycotoxin. Consequently, it should be considered as an additional masked form of zearalenone with potential relevance for food safety.

β-Glucosidase activities of lactic acid bacteria: mechanisms, impact on fermented food and human health

Through the hydrolysis of plant metabolite glucoconjugates, β-glucosidase activities of lactic acid bacteria (LAB) make a significant contribution to the dietary and sensory attributes of fermented food. Deglucosylation can release attractive flavour compounds from glucosylated precursors and increases the bioavailability of health-promoting plant metabolites as well as that of dietary toxins. This review brings the current literature on LAB β-glucosidases into context by providing an overview of the nutritional implications of LAB β-glucosidase activities. Based on biochemical and genomic information, the mechanisms that are currently considered to be critical for the hydrolysis of β-glucosides by intestinal and food-fermenting LAB will also be reviewed.

IS30 elements are mediators of genetic diversity in Oenococcus oeni

Oenococcus oeni is responsible for the malolactic fermentation of wines. Genomic diversity has been recently established in the species and extensive attention is now being given to the genomic bases of strain-specific differences. We explored the role of insertion sequences (IS), which are considered as driving forces for novel genotypic and phenotypic variants in prokaryotes. The present study focuses on members of the IS30 family, which are widespread among lactic acid bacteria. An in silico analysis of the three available genomes of O. oeni in combination with the use of an inverse PCR strategy targeting conserved IS30-related sequences indicated the presence of seven IS30 copies in the pangenome of O. oeni. A primer designed to anneal to the conserved 3' end of the IS30 element was paired with each of the seven primers selected to bind to unique sequences upstream of each of the seven mobile elements identified. The study presents an overview of the abundance, and the genomic environment of IS30 elements in the O. oeni pangenome and shows that the two existing genetic sub-populations previously described in the species through multilocus sequence typing analysis (MLST) differ in their IS30 content. Possible IS30 impacts on bacterial adaptation are discussed.

Characterization of two distinct glycosyl hydrolase family 78 alpha-L-rhamnosidases from Pediococcus acidilactici

α-L-Rhamnosidases play an important role in the hydrolysis of glycosylated aroma compounds (especially terpenes) from wine. Although several authors have demonstrated the enological importance of fungal rhamnosidases, the information on bacterial enzymes in this context is still limited. In order to fill this important gap, two putative rhamnosidase genes (ram and ram2) from Pediococcus acidilactici DSM 20284 were heterologously expressed, and the respective gene products were characterized. In combination with a bacterial β-glucosidase, both enzymes released the monoterpenes linalool and cis-linalool oxide from a muscat wine extract under ideal conditions. Additionally, Ram could release significant amounts of geraniol and citronellol/nerol. Nevertheless, the potential enological value of these enzymes is limited by the strong negative effects of acidity and ethanol on the activities of Ram and Ram2. Therefore, a direct application in winemaking seems unlikely. Although both enzymes are members of the same glycosyl hydrolase family (GH 78), our results clearly suggest the distinct functionalities of Ram and Ram2, probably representing two subclasses within GH 78: Ram could efficiently hydrolyze only the synthetic substrate p-nitrophenyl-α-L-rhamnopyranoside (V(max) = 243 U mg(-1)). In contrast, Ram2 displayed considerable specificity toward hesperidin (V(max) = 34 U mg(-1)) and, especially, rutinose (V(max) = 1,200 U mg(-1)), a disaccharide composed of glucose and rhamnose. Both enzymes were unable to hydrolyze the flavanone glycoside naringin. Interestingly, both enzymes displayed indications of positive substrate cooperativity. This study presents detailed kinetic data on two novel rhamnosidases, which could be relevant for the further study of bacterial glycosidases.

Heterologously expressed family 51 alpha-L-arabinofuranosidases from Oenococcus oeni and Lactobacillus brevis

Putative α-L-arabinofuranosidases of Oenococcus oeni and Lactobacillus brevis were heterologously expressed and characterized. We report the basic functional properties of the recombinant enzymes in comparison to those of a commercial family 51 arabinosidase of Aspergillus niger.