Hydrogen sulphide production during cider fermentation is moderated by pre‐fermentation methionine addition

Yeast assimilable nitrogen (YAN) concentration and composition impact hydrogen sulphide (H₂S) production and fermentation kinetics during wine fermentation, but this phenomenon has not been extensively studied in cider fermentation. Our hypothesis was that H₂S production during cider fermentation could be decreased through pre‐fermentation modification of concentrations of individual amino acids. Apple juice (53 mg L⁻¹ YAN) was supplemented with asparagine, arginine, methionine or ammonium and fermented with EC1118 and UCD522 yeast strains. No difference in H₂S production among fermentations was observed with addition of asparagine, arginine or ammonium. Methionine addition of 5 mg L⁻¹ decreased H₂S production by yeast strain EC1118 at 53 mg L⁻¹ YAN. With 153 mg L⁻¹ initial YAN, only methionine addition of 50 mg L⁻¹ decreased H₂S production, and no tested methionine rates decreased H₂S production with 253 mg L⁻¹ initial YAN. Supplementation to 153 mg L⁻¹ YAN resulted in increased H₂S production at all methionine concentrations tested. Sensory differences in aroma were detected in samples supplemented with ammonium and methionine, and these differences were correlated with observed differences in H₂S production. Our results indicate that supplementing cider fermentations with methionine leads to lower H₂S formation, especially in apple juice containing low YAN. © 2017 The Authors Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling     

Variation in content of tyramine,histamine, 2-phenylethylamine,tryptamine and their precursor amino acids in a Chardonnay wine by using different commercial active dry yeasts and nitrogen sources

Wine is a fermented beverage that could be affected by high concentrations of biogenic amines, thus altering organoleptic and health properties. In this work, the capacity of different selected yeast strains regarding to affect the content of tyramine, histamine, 2-phenylethylamine, tryptamine and their precursor amino acids (pAA) during fermentation has been described. Overall, biogenic amines (BAs) and pAA contents appeared significantly related both to the strain and to the nutrient supplementation applied. Among BAs, without and (with) nitrogen source addition, the concentrations covered a range between 0.1 and 9.5 (0.1–10.3) mg L⁻¹ for tyramine; 0.1 and 4.4 (0.1–4.6) mg L⁻¹ for histamine; 0.4 and 1.1 (0.4–1.4) mg L⁻¹ for 2-phenylethylamine; and 0.02 and 0.14 (0.01–0.12) mg L⁻¹ for tryptamine, respectively. Considering that also wine yeast species are responsible for BAs formation, the evidence from fermentation trials underlined the relevance of a careful choice of ADY strains and nitrogen sources in the management of alcoholic fermentation in wine.     

The glycerol and ethanol production kinetics in low-temperature wine fermentation using Saccharomyces cerevisiae yeast strains

Increasing glycerol production in low-temperature wine fermentation is of concern for winemakers to improve the quality of wines. The objective of this study was to investigate the effect of 10 different Saccharomyces cerevisiae on the kinetics of production of glycerol, ethanol and the activities of glycerol-3-phosphate dehydrogenase (GPD) and alcohol dehydrogenase (ADH) in low-temperature fermentation. Ethanol production was influenced by temperature, and it was slightly higher at 13 °C than at 25 °C. Glycerol yields were significantly affected by both temperature and strains. More glycerol was produced at 25 °C than at 13 °C because the activity of GPD was higher at 25 °C than at 13 °C. Glycerol production of the different yeast strains was up to 3.19 and 3.18 g L⁻¹ at 25 and 13 °C, respectively. Therefore, isolating the yeast strains with high glycerol production and adaptation to low-temperature fermentation is still the best method in winemaking.     

Effects of sugar concentration on mango wine composition fermented by Saccharomyces cerevisiae MERIT.ferm

This study investigated the effect of initial sugar concentrations (^°Brix of 17, 23 and 30) on mango wine composition fermented by Saccharomyces cerevisiae MERIT.ferm. It was found that growth rate and maximum cell population were inversely correlated with initial sugar levels with the fastest growth rate and largest cell population in the low sugar fermentation. However, the cell population in the low and medium sugar fermentation declined significantly (from 8.7 and 8.2 log to 2 and 2.8 log, respectively) relative to the high sugar fermentation in which cell populations remained stable upon reaching the stationary phase (7.7 log). Glycerol production increased with increasing sugar content in low (13.4 g L^?1), medium (14.5 g L^?1) and high (15.9 g L^?1) sugar fermentation. In addition, high sugar fermentation had a negative impact on volatile production with significantly lower amounts of acetate esters (1.5 mg L^?1) but more acetic acid (0.54 g L^?1) compared to the low (5.0 mg L^?1 and 0.44 g L^?1, respectively) and medium (3.7 mg L^?1 and 0.49 g L^?1, respectively) sugar fermentations. Furthermore, volatiles especially terpene hydrocarbons (α‐caryophyllene was released) present in mango juice were significantly metabolised after fermentation, while numerous new volatile compounds (such as isobutyl alcohol, isoamyl alcohol, ethyl and acetate esters) were produced. Some terpene alcohols were released and converted into corresponding acetyl esters. This may indicate that the mango wines fermented with different levels of sugars would have different flavour aromas.     

Microbiological assay with Bacillus licheniformis for the easy detection of quinolones in milk

This paper proposes a microbiological method in microtitre plates for the detection of residues of quinolones in milk. The method uses spores of Bacillus licheniformis in culture medium with a redox combination of indicators and gives a response time of 5.5 h. This method detects 92 μg L⁻¹ of ciprofloxacin, 63 μg L⁻¹ of danofloxacin, 109 μg L⁻¹ of enrofloxacin, 101 μg L⁻¹ of marbofloxacin and 109 μg L⁻¹ of sarafloxacin in milk. Therefore, the assay is easy to develop and to use in laboratory, allowing analysis of large numbers of samples at low cost. Due to its good sensitivity to quinolones, this assay can be used as a complementary test of commercial microbiological methods and thereby improve food security.     

Physicochemical and microbiological description of Caxiri – a cassava and corn alcoholic beverage

Caxiri is a fermented alcoholic beverage made from cassava, corn and sweet potatoes by indigenous people in Brazil. Saccharomyces cerevisiae Rhodotorula mucilaginosa, Lactobacillus fermentum, Bacillus subtilis and L. helveticus were the main microbial species detected. Maltose was the main carbohydrate found (19.12 g L^?1), and lactic acid (15.09 g L^?1) and ethanol (92.16 g L^?1) were also found in high concentrations. Gas chromatography‐flame ionisation detector was used to identify thirteen volatile compounds. Among these volatiles, the higher concentrations were decanoic acid (123.04 μg L^?1) for the acids, diethyl malate (88.32 μg L^?1) for the esters, furfural (109.31 μg L^?1) for the aldehydes, 2‐phenylethanol (1022.76 μg L^?1) for the alcohols and 1,1‐diethoxyethane (226.24 μg L^?1) for the others. This study contributes to increasing knowledge of the microbiota present in the alcoholic fermentation produced from cassava, corn and sweet potatoes.     

The application of near‐infrared spectroscopy in beer fermentation for online monitoring of critical process parameters and their integration into a novel feedforward control strategy

Traditional methods used in the analysis of fermentation media suffer from a number of limitations. The search for more rapid and efficient methods has led to the development and application of near‐infrared spectroscopy. Near‐infrared spectroscopy has been applied successfully in a variety of industrial processes: agricultural, food, chemical and pharmaceutical, generally in the areas of raw material quality control but also including intermediate and finished product testing. The present research explores its potential for online fermentation monitoring of total cell count (TCC), specific gravity (SG), free amino nitrogen (FAN) and percentage alcohol by volume (% v v⁻¹) in a 300 L pilot‐scale validation batch. Models that were generated from three calibration batches for each of these constituents exhibited overall favourable standard error of cross validation (SECV) and fit of predicted vs actual cross validated results (SECV, R ²): SG (0.00072, 0.995), ethanol (0.17% v v⁻¹, 0.990), FAN (16.5 mg L⁻¹, 0.886) and TCC (1.24 × 10⁶ cells mL⁻¹, 0.640). The data that was most relevant to cell metabolism was determined to be sugar consumption rate, ethanol production rate, yield of ethanol and fermentation lag time. These ‘critical performance parameters’ were incorporated into a novel feed‐forward control strategy where yeast pitching rate was modified based on values of the critical performance parameters from the previous batch. Use of this feed‐forward strategy demonstrated how brewers can utilize near‐infrared monitoring for quality assurance through early detection of shifts in fermentation performance. Copyright © 2017 The Institute of Brewing & Distilling     

Evaluation of various Bacillus coagulans isolates for the production of high purity L-lactic acid using defatted rice bran hydrolysates

Defatted rice bran (DRB) constitutes an abundant by-product stream, generated during rice milling and subsequent bran oil extraction. Enzymatic hydrolysis of starch and protein content in DRB was optimised in terms of solid loading. Among the four solid loadings evaluated (10%, 15%, 20% and 25%), the hydrolysate derived from 20% solids resulted in the highest concentration of glucose (82.3 g L⁻¹) and free amino nitrogen (234.8 mg L⁻¹). The fermentability of the hydrolysate was evaluated via screening of sixteen isolates. All the strains were able to grow and produce high purity L-lactic acid, utilising the DRB as sole carbon and nutrient source. Among the studied strains, the Bacillus coagulans A107 isolate presented the most promising results in terms of final lactic acid concentration (75.9 g L⁻¹), yield (0.90 g g⁻¹) and productivity (2.7 g L⁻¹ h⁻¹). The results of this study indicate that DRB could be employed as an inexpensive, alternative substrate for L-lactic acid production.     

Comparison of the effect of pulsed electric field or high voltage electrical discharge for the control of sweet white must fermentation process with the conventional addition of sulfur dioxide

The present work discusses the efficiency of pulsed electrical treatments for the inactivation of yeasts. The application of pulsed electric fields (PEFs) and high voltage electrical discharges (HVEDs) as alternatives to sulfites, which are used as anti-microbial to stop the fermentation of sweet white wine, was investigated. The influence of sulfite concentration (from 0 mg·L^− 1 to 500 mg·L^− 1), PEF (from 4 kV·cm^− 1 to 20 kV·cm^− 1; from 0.25 ms to 6 ms) and HVED (40 kV/cm; 1 ms or 4 ms) treatments on the inactivation of total yeasts and non-Saccharomyces yeasts was determined. The addition of SO₂ (250 mg·L^− 1) resulted in 8 log total yeast reduction. The maximum yeast inactivation obtained with PEF and HVED was respectively 3 and 4 logs. The use of SO₂, HVED and PEF allows decreasing the non-Saccharomyces yeast level by 7, 5 and 4 logs respectively. However, the wine browning was less pronounced for the samples treated by PEF in comparison with HVED and SO₂ treatments. PEF seems to be the most suitable alternative technique to sulfite addition.     

Effect of debittering and solid-state fermentation processes on the nutritional content of lupine (Lupinus mutabilis Sweet)

There is a growing interest in vegetable-based sources of proteins. Despite its high nutrient content, lupine has been rarely exploited as a protein source due to the presence of high levels of non-nutritive compounds such as alkaloids, which impart a bitter taste. Here, we evaluated the effect of debittering and solid-state fermentation on the nutritional contents of three lupine varieties (Lupinus mutabilis Sweet). These processes induced significant changes (P < 0.05) in the nutritional composition of the three lupine varieties (INIAP-450, INIAP-451 and Criollo) and increased the protein levels to 644.55 g kg⁻¹ (Criollo variety) and the levels of several constituent amino acids such as valine (54.62 g kg⁻¹), methionine (42.47 g kg⁻¹), isoleucine (59.27 g kg⁻¹) and leucine (76.32 g kg⁻¹). The ether extract of INIAP-450 showed increased levels (up to 244.03 g kg⁻¹); especially, monounsaturated fatty acids (559.78 g kg⁻¹) and polyunsaturated fatty acids (293.17 g kg⁻¹) were observed. The omega-6/omega-3 ratio in the debittered grain oil reached the minimum requirement established for good-quality oils (5/1). However, the levels of other components decreased, showing levels up to 13.04 g kg⁻¹ (total starch) in the Criollo variety, 22.62 g kg⁻¹ (resistant starch) in INIAP-450, 6.53 g kg⁻¹ (potassium) in INIAP-451, 46 g kg⁻¹ (iron) in INIAP-451 and 29.75 g kg⁻¹ (zinc) in INIAP-450.     

Overexpression of vacuolar H+‐ATPase‐related genes in bottom‐fermenting yeast enhances ethanol tolerance and fermentation rates during high‐gravity fermentation

Vacuolar H⁺‐ATPase (V‐ATPase) is thought to play a role in stress tolerance. In this study it was found that bottom‐fermenting yeast strains, in which the V‐ATPase‐related genes DBF2, VMA41/CYS4/NHS5 and RAV2 were overexpressed, exhibited stronger ethanol tolerance than the parent strain and showed increased fermentation rates in a high‐sugar medium simulating high‐gravity fermentation. Among the strains examined, the DBF2‐overexpressing bottom‐fermenting yeast strain exhibited the highest ethanol tolerance and fermentation rate in YPM20 medium. Using this strain, high‐gravity fermentation was performed by adding sugar to the wort, which led to increased fermentation rates and yeast viability compared with the parent strain. These findings indicate that V‐ATPase is a stress target in high‐gravity fermentation and suggests that enhancing the V‐ATPase activity increases the ethanol tolerance of bottom‐fermenting yeast, thereby improving the fermentation rate and cell viability under high‐gravity conditions. Copyright © 2012 The Institute of Brewing & Distilling     

Comparative study of physiological adaptation to salt stress in the genome shuffled Candida versatilis and a wild-type salt-tolerant yeast strain

Candida versatilis is a yeast with a complex salt-tolerant system. It can maintain normal physiological activities and metabolic fermentation under a high-salt environment. The cellular mechanisms of adaptation to salt stress in strains of a wild type of C. versatilis (WT) and S3–5, genome shuffling strains of C. versatilis with improved tolerance to salt, were investigated. The content of intra- and extra-cellular glycerol, intra-cellular Na⁺, as well as membrane fluidity and permeability, were determined under salt-stressed yeast growth conditions. The results showed that Na⁺/H⁺-antiporter played a primary role in Na⁺ extrusion and H⁺-ATPase has been associated with yeast survival under salt stress. Considerable amounts of glycerol were produced and secreted by the yeast to outside the cell under this salt stress. Changes in the portion of membrane saturated and unsaturated fatty acid composition of C. versatilis in response to osmotic stress lead to membrane permeability and fluidity decreases. They could restrict the influx of Na⁺, enhance H⁺-ATPase activity, and prevent leakage of glycerol across the cell membrane under osmotic stress. The salt tolerance of genome shuffled strain S3–5 was higher than WT. It could be correlated with a higher level of intra-cellular accumulation of glycerol and sodium ions in cells of S3–5 than WT as well as a higher portion of oleic fatty acid (C18: 1) and a lower level of linoleic acid (C18: 2) in cell membranes of the studied yeast mutant. It can be concluded that S3–5 improved physiological regulatory mechanisms of response to salt stress, such as decreased membrane fluidity and a permeability that rapidly adjusted to osmotic stress.     

Influence of fermentation parameters on phytochemical profile and volatile properties of mulberry (Morus nigra) wine

In the present study Box–Behnken Design was employed to analyse the effects of fermentation parameters such as temperature (T _F), pH, inoculum size (I _S) and °Brix (B_X) on total phenolic concentration (TPC), total flavonoid concentration (TFC), total anthocyanin concentration (TAC), ethanol concentration (ETHC), total higher alcohol concentration (THAC) and total ester concentration (TESC) for the development of a phytochemical‐rich wine using mulberry as a substrate. The results demonstrated that fermentation parameters significantly alter the wine characteristics. Hence, a wine with excellent consumer preference (overall acceptability of 8.51) and high concentration of phytochemicals (TPC = 6014.03 ± 27.80 mg L⁻¹, TFC = 4791.35 ± 21.22 mg L⁻¹, TAC = 1480.72 ± 5.33 mg L⁻¹) as well as good aromatic properties (ETCH =82.85 ± 0.87 g L⁻¹, THAC =249.91 ± 0.31 mg L⁻¹ and TESC =52.55 ± 0.17 mg L⁻¹) with high antioxidant activity (DPPH =220.18 mmol·l⁻¹) was obtained at optimized fermentation conditions of T _F = 25°C, pH = 4.00, I _S = 10% (v /v) and B_X = 26. The results from the present study might contribute to strengthening the development of wine containing high concentrations of phytochemical compounds with attractive olfactory attributes. Copyright © 2017 The Institute of Brewing & Distilling     

Mixed fermentation of jujube juice (Ziziphus jujuba Mill.) with L. rhamnosus GG and L. plantarum-1: effects on the quality and stability

This study was conducted aiming at improving the quality of jujube juice by mixed fermentation of lactobacilli. Selection of favourable lactobacilli and addition of nitrogen sources were explored as an efficient method to improve the viability of probiotic in jujube juice. After fermentation, the viability increased to 9.15 ± 0.10 Log CFU mL⁻¹, while the content of lactic acid increased to 5.61 ± 0.03 mg mL⁻¹. The total phenolic and total flavonoid content were 2663.03 ± 11.95 μg mL⁻¹ and 163.95 ± 0.47 μg mL⁻¹ respectively. Moreover, the stability of fermented jujube juice during refrigeration was investigated, which showed that the viability dropped to 8.84 ± 0.6 Log CFU mL⁻¹ and the concentration of lactic acid slowly increased to 6.51 ± 0.04 mg mL⁻¹; the ABTS value showed a 4.26% reduction and FRAP value did not significantly (P < 0.05) change during refrigerated storage. In addition to the existing knowledge, our data aid to the future applications of the jujube as a potential ingredient in novel probiotic foods formulation.     

Co‐inoculation of yeast and lactic acid bacteria to improve cherry wines sensory quality

This study examined the effect of co‐inoculation of yeast and lactic acid bacteria (LAB) on the chemical and sensory characteristics of cherry wines, in comparison with a traditional sequential culture. Three LABs were investigated, including two O. oeni (SG26 and Viniflora) and one L. plantarum (PL18). All co‐inoculations significantly shortened the fermentation time (average 8 days earlier) to reach a stable level of residual sugar (<2 g L^?1) and L‐malic acid (<0.5 g L^?1), and no inhibitory effect on the yeast proliferation was observed. For volatiles determined, co‐culture with SG26 produced the greatest amount of volatile components (138.5 mg L^?1), whereas sequential inoculation with PL18 had the lowest level (119.6 mg L^?1). PCA result revealed that different LABs had diverse influences on the volatile profile of cherry wines, and sensory analysis confirmed that these samples presented distinct sensory profiles, and particularly, a stronger note of fruity was perceived when co‐culture was used.     

Wine lees valorization: Biorefinery development including production of a generic fermentation feedstock employed for poly(3-hydroxybutyrate) synthesis

This study demonstrates the development of a novel wine lees (WL) based integrated biorefinery for the production of several added-value products. WL were initially fractionated for the production of antioxidants, tartrate and ethanol and the remaining stream was converted into a fermentation nutrient supplement for poly(3-hydroxybutyrate) (PHB) production using the strain Cupriavidus necator DSM 7237. Hydrolysis of pretreated WL was carried out using crude enzyme consortia produced via solid state fermentation of Aspergillus oryzae. Optimization of hydrolysis was based on the enhancement of total Kjeldahl nitrogen to free amino nitrogen (FAN) conversion yield by evaluating the effect of the initial pH value, temperature, initial proteolytic activity and initial WL concentration. WL hydrolysates and crude glycerol were used as nutrient and carbon sources, respectively, in batch and fed-batch fermentations for the production of PHB. Bacterial growth and PHB production were influenced significantly by the FAN content of the WL derived hydrolysates and by the addition of trace elements. Using an initial FAN concentration of 700 mg L^− 1 and supplementation with trace elements led to the production of 30.1 g L^− 1 of PHB concentration with an intracellular content of 71.3% (w w^-1) and a productivity of 0.56 g L^− 1 h^− 1 during fed-batch fermentation.     

Optimization of the culture medium composition using response surface methodology for new recombinant cyprosin B production in bioreactor for cheese production

The optimization of culture medium composition was carried out for improvement the recombinant cyprosin B production, an enzyme with high milk-clotting activity. Response surface methodology (RSM) was applied to evaluate the effect of variables namely glucose, yeast extract (YE) and bactopeptone present in the culture medium, used for recombinant cyprosin B production by transformed Saccharomyces cerevisiae BJ1991 strain in shake-flask and bioreactor culture conditions. The central composite experimental design (CCD) was adopted to derive a statistical model for optimizing the composition of the fermentation medium. The optimal concentration estimated for each variable related to a theoretical maximum of cyprosin B activity (488 U mL⁻¹) was 30 g L⁻¹ glucose, 15 g L⁻¹ YE and 27 g L⁻¹ bactopeptone. The optimized medium composition, based on empirical model, led to a cyprosin B activity of 519 U mL⁻¹, which corresponds to an increase of 46%. The fermentation using optimized culture medium in a 5-L bioreactor allowed a significant increase in biomass (82%) and recombinant cyprosin B production (139%). The improvement in the recombinant cyprosin B production after optimization process can be considered adequate for large-scale applications, and the clotting activity of cyprosin B account for their use in industrial cheese making.     

Ethanol tolerance of five non-Saccharomyces wine yeasts in comparison with a strain of Saccharomyces cerevisiae—influence of different culture conditions

The kinetics of cell inactivation at high concentrations of ethanol (22.5% and 25% v v⁻¹) was studied with particular reference to the influence of different cultivation conditions (aerobiosis, semi-aerobiosis, anaerobiosis, addition of survival factors) prior to ethanol challenge. The levels of fatty acids and sterols in cells grown under these different conditions were analysed in order to derive a potential relationship between the ethanol tolerance and the lipid composition of the different strains studied. Under the conditions tested, Hanseniaspora guilliermondii showed an ethanol tolerance very similar to that of Saccharomyces cerevisiae, and very different to that of the other apiculate yeast, H. uvarum. The survival of S. cerevisiae and H. guilliermondii at 25% (v v⁻¹) ethanol was strongly influenced by the conditions of cultivation prior to the ethanol challenge. A small increase in survival was observed for H. uvarum and Torulaspora delbrueckii in the cultures grown in aerobiosis. Growth of these yeasts in anaerobiosis in the presence of added ergosterol and Tween 80 (as a source of oleic acid) did not induce a considerable tolerance to the ethanol challenge, in spite of the incorporation of these compounds by the cells. In these growth conditions Debaryomyces hansenii was not capable of incorporating the survival factors and did not increase the ethanol tolerance. It is shown in this work that, besides S. cerevisiae, the presence of oxygen and the addition of survival factors to the culture conditions and the subsequent increase in the proportion of cell sterols and unsaturated fatty acids may play an important role in the ethanol tolerance of some non-Saccharomyces yeasts. This effect was not, however, observed in all of the yeasts studied.     

Galacto-oligosaccharide synthesis using chemically modified β-galactosidase from Aspergillus oryzae immobilised onto macroporous amino resin

The goal of this study was to establish an efficient immobilisation protocol for β-galactosidase from Aspergillus oryzae onto the polystyrenic macroporous resin Purolite^® A-109 for better utilisation of its transglactosylation activity and application in galacto-oligosaccharide (GOS) synthesis. This was achieved by improving simple ionic adsorption by carboxyl group activation on the enzyme surface with carbodiimide, enabling covalent immobilisation. This yielded significantly increased operational stability, assayed as GOS synthesis, in a batch reactor, and even more prominently, in a fluidised bed reactor (73% activity retained after 10 cycles). The immobilised enzyme showed two very beneficial advantages over the free enzyme for future applications: higher affinity towards catalysing transgalactosylation than towards hydrolysis and shift of pH optimum towards more acidic conditions. GOS synthesis performed under the optimum conditions obtained (400 g L⁻¹ lactose, pH 4.5, 50 °C) yielded 87 g L⁻¹ and 100 g L⁻¹ for batch and fluidised bed reactors, respectively.