Williopsis Saturnus Var Research Articles

Fermentation characteristics of four non-Saccharomyces yeasts in green tea slurry

The fermentation characteristics of non-Saccharomyces yeasts (Pichia kluyveri FrootZen, Torulaspora delbrueckii Prelude, Williopsis saturnus var. mrakii NCYC2251 and Torulaspora delbrueckii Biodiva) were evaluated in green tea slurry fermentation. Each yeast showed different fermentation performances: strains Prelude and Biodiva utilized sucrose faster than the other two yeasts; strain NCYC2251 was the only species that metabolized xylose. Strain FrootZen increased the caffeine content significantly and strain Prelude showed the opposite trend, both at a statistical level, while theanine contents in four samples were relatively stable. Biodiva and FrootZen significantly improved polyphenols content and the oxygen radical absorbance capacity of fermented teas. Some endogenous volatiles such as ketones, lactones and aldehydes decreased to lower or undetected levels, but one of the key tea aroma compounds methyl salicylate increased by 34-fold and 100-fold in P. kluyveri and W. saturnus samples respectively. Therefore, green tea fermentation by appropriate non-Saccharomyces yeasts can enhance its antioxidant capacity and alter the aroma compound profile.

Effects of edible coating containing Williopsis saturnus var. saturnus on fungal growth and aflatoxin production by Aspergillus flavus in peanuts

AbstractProduction of aflatoxin by Aspergillus flavus in peanuts is both a health hazard and major problem. This study investigated the ability of a whey protein concentrate (WPC)‐based edible coating containing Williopsis saturnus var. saturnus to prevent growth of A. flavus and aflatoxin production in peanuts. WPC with/without W. saturnus (7 log colony‐forming unit [CFU]/g) or W. saturnus alone was sprayed on peanuts inoculated with A. flavus (3 log CFU/g) and stored for 84 days at 25°C. Application of coating with W. saturnus reduced both growth of A. flavus and aflatoxin level by 82 and 69.5% compared with the control, respectively. Thiobarbituric acid values were around 60% lower in peanuts coated with WPC compared with the control. Sensory and chemical properties of peanuts were not significantly affected by coating treatment (p < .05). Based on results, coating with W. saturnus appears useful in preventing both growth of A. flavus and aflatoxin production in peanuts.Practical ApplicationsImproved WPC based coating containing W. saturnus can be applied on surface of roasted peanuts to prevent growth of A. flavus and aflatoxin production.

Determination of Antifungal Effect of Edible Coatings Containing Williopsis saturnus var. saturnus Against Yeast and Mold Growth on Kashar Cheese.

One of the most important problems of Kashar cheese producers is mold and yeast spoilage during storage. Williopsis saturnus var. saturnus killer yeast has been reported to have an antagonistic effect on mold and yeast reproduction. In this study, the antifungal effect of a whey protein concentrate (WPC) coating containing W. saturnus was investigated in Kashar cheese. WPC with or without W. saturnus (7 log CFU/g) or W. saturnus without coating was applied on the surface of Kashar cheese samples and stored at 4 °C for 56 days. Microbiological, chemical, physical and sensory properties of cheese samples were assessed.After 56 days of storage, the numbers of lactic acid bacteria were not affected by WPC containing W. saturnus; however,the population of W. saturnus increased by 1 log CFU/g. Application of W. saturnus reduced the growth of other yeasts and molds (P < 0.05). Chemical, physical and sensory properties of all coated cheeses remained unchanged. In a conclusion, use of WPC coatings containing W. saturnus can potentially minimize mold and yeast spoilage of cheese during storage.

Antifungal, Mechanical, and Physical Properties of Edible Film Containing Williopsis saturnus var. saturnus Antagonistic Yeast.

The molding of food products causing health risks is a main problem in the food industry. In this study, as an alternative solution for preventing mold growth, an antifungal edible film was developed by incorporating Williopsis saturnus var. saturnus (0; 3; 7; and 9 logs CFU/cm2 ) into whey protein concentrate (WPC) based films. Antifungal properties of the films against Penicilium expansum and Aspergillus niger were analyzed using the disc diffusion method. Physical (barrier, solubility, color), mechanical (tensile strength and percent elongation) properties of the films as well as the survival of W. saturnus in the film were assessed during 28 days of storage at 23 °C. According to the results, the viability of W. saturnus (7 and 9 logs CFU/cm2 ) in WPC films stored for 28 days under vacuum or non-vacuum decreased to 36% and 60%, respectively. In addition, films containing W. saturnus decreased the viability of P. expansum and A. niger by 29% and 19%, respectively. Adding yeast did not change the tensile strength (P > 0.05), but significantly decreased % elongation and increased water vapor and oxygen permeability and water solubility (P < 0.05). In conclusion, this study showed that the developed films may be useful for inhibiting mold growth on foods.

Modulation of grape wine flavor via the sequential inoculation of Williopsis saturnus and Saccharomyces cerevisiae

ABSTRACTThe effects of the inoculum ratio of Williopsis saturnus var. saturnus NCYC22 and Saccharomyces cerevisiae var. bayanus EC-1118 at 1:200 and 1:800 on the chemical and volatile compositions of grape wine were studied in sequential fermentation. The grape juice was first inoculated with Williopsis (W.) saturnus for 9 d; thereafter, Saccharomyces (S.) cerevisiae was inoculated to continue the fermentation until d 19. The cell population of W. saturnus disappeared by d 13, with S. cerevisiae dominating until the end of the fermentation in both inoculum ratios. The changes in yeast count, pH, total soluble solids, sugars, organic acids, and amino acids were similar between the two inoculum ratios. A range of volatile compounds was formed, including alcohols, esters, fatty acids, aldehydes, and terpenes. There were significant differences between both inoculum ratios for medium-chain fatty acids (C8, C10, and C12), ethyl esters of fatty acids of C6, C10, C12, and C14 as well as isoamyl octanoate, while other volatiles were statistically the same.

Effects of different inoculation strategies of Saccharomyces cerevisiae and Williopsis saturnus on chemical components of mango wine

This study investigated the effects of different inoculation strategies of Saccharomyces cerevisiae MERIT.ferm and Williopsis saturnus var. mrakii NCYC 500 on volatile composition of mango wine. The inoculation strategies involved positive sequential fermentation (PSF, W. saturnus NCYC 500 was first inoculated for 14 days before inactivation, then S. cerevisisae MERIT.ferm was inoculated and fermentation continued for another 7 days), negative sequential fermentation (NSF, S. cerevisiae MERIT.ferm was first inoculated for 7 days before inactivation; after that, W. saturnus NCYC 500 was inoculated at day 14 followed by another 7 days fermentation) and simultaneous mixed culture fermentation (MCF). The growth of S. cerevisiae MERIT.ferm in PSF declined slightly immediately after inoculation, which differed from that in NSF and MCF. On the other hand, the growth of W. saturnus NCYC 500 was inhibited by prior growth of S. cerevisiae MERIT.ferm in NSF and MCF. The volatile profiles of the mango wines varied significantly among different inoculation strategies. PSF produced higher amounts of desirable volatile compounds especially ethyl esters (ethyl esters of hexanoate, decanoate, octanoate), acetate esters (ethyl acetate, isobutyl acetate, isoamyl acetate and 2-phenylethyl acetate) and isoamyl alcohol, which could contribute more fruity and creamy notes to the wines. Therefore, PSF would be a useful strategy for fruit wine making with more complex aroma.

Retraction: Influence of Temperatures and Fermentation Behavior of Mixed Cultures of Williopsis saturnus var. saturnus and Saccharomyces cerevisiae Associated with Winemaking

Retraction: Influence of Temperatures and Fermentation Behavior of Mixed Cultures of Williopsis saturnus var. saturnus and Saccharomyces cerevisiae Associated with Winemaking

Effect of L-isoleucine and L-phenylalanine Addition on Aroma Compound Formation During Longan Juice Fermentation by a Co-culture of Saccharomyces cerevisiae and Williopsis saturnus

Some amino acids are known to be precursors of aroma-active compounds produced by yeast metabolism. This study examined the effect of the addition of L-isoleucine and L-phenylalanine on the volatile profiles of longan wine fermented by a co-culture of Saccharomyces cerevisiae var. bayanus EC-1118 and Williopsis saturnus var. saturnus CBS254 inoculated at a ratio of 1:1 000 cfu/mL with the aim of enhancing longan wine aroma. Significantly higher concentrations of active amyl alcohol (2-methyl-1-butanol), 2-phenylethyl alcohol and their corresponding acetate esters were found in the longan wine with added L-isoleucine and L-phenylalanine respectively, compared with the control (without added amino acids). The biosynthesis of other volatile compounds was either similar or minimally different, although the formation of some acetate esters, such as isoamyl acetate, hexyl acetate and ethyl acetate, was decreased. These results suggest that the added amino acids play an important role in enhancing the production of targeted aroma compounds in longan wine fermented with mixed yeasts, and that the addition of selected amino acids can be a valuable tool to modulate the formation of aroma compounds in longan wine.

Impact of Amino Acid Addition on Aroma Compounds in Papaya Wine Fermented with Williopsis mrakii

The impact of amino acid addition on aroma compound formation in papaya wine fermented with yeast Williopsis saturnus var. mrakii NCYC2251 was studied. Time-course papaya juice fermentations were carried out using W. saturnus var. mrakii NCYC2251, with and without the addition of selected amino acids (L-leucine, L-isoleucine, L-valine and L-phenylalanine). Yeast growth and changes in sugars, °Brix, organic acids and pH were similar, regardless of amino acid addition. L-Leucine addition increased the production of isoamyl alcohol and some esters such as isoamyl acetate, isoamyl butyrate and isoamyl propionate, while L-isoleucine addition increased the production of active amyl alcohol and active amyl acetate. L-valine addition slightly increased the production of isobutyl alcohol and isobutyl acetate. L-phenylalanine addition increased the formation of 2-phenylethanol, 2-phenylethyl acetate and 2-phenylethyl butyrate, while decreasing the production of most other esters. This study suggests that papaya juice fermentation with W. saturnus var. mrakii NCYC2251 in conjunction with the addition of selected amino acid(s) can be an effective way to modulate the aroma of papaya wine.

Evaluation of Beer Fermentation with a Novel Yeast Williopsis saturnus.

The aim of this study is to evaluate the potential of a novel yeast Williopsis saturnus var. mrakii NCYC 500 to produce fruity beer. Fermentation performance of W. mrakii and beer volatile composition were compared against that fermented with Saccharomyces cerevisiae Safale US-05. oBrix, sugar and pH differed significantly between the two types of beer. A total of 8 alcohols, 11 acids, 41 esters, 9 aldehydes, 8 ketones, 21 terpenes and terpenoids, 5 Maillard reaction products and 2 volatile phenolic compounds were detected. Yeast strain Safale US-05 was more capable of producing a wider range of ethyl and other esters, while yeast strain NCYC 500 produced significantly higher amounts of acetate esters. Strain NCYC 500 retained more terpenes and terpenoids, suggesting that the resultant beer could possess more of the aromatic hint of hops. This study showed that W. saturnus var. mrakii NCYC 500 could ferment wort to produce low-alcohol beer with higher levels of acetate esters, terpenes and terpenoids than yeast S. cerevisiae Safale US-05.

Enhancement of bifidobacteria survival by Williopsis saturnus var. saturnus in milk.

The viability of three strains of probiotic Bifidobacterium lactis that were inoculated into UHT milk was examined with and without the presence of the yeast, Williopsis saturnus var. saturnus NCYC 22, in polypropylene tubes at 30 °C. The B. lactis viable cell count for strains HN019 and BB-12 remained above 6.0 Log cfu/ml, while strain B94 had 5.7 Log cfu/ml after six weeks of incubation in the presence of the co-inoculated yeast. Incubating the bifidus milk without added yeast under anaerobic condition did not improve the survival of B. lactis HN019, indicating that oxygen removal may not be responsible for W. saturnus NCYC 22's viability enhancing property. The addition of yeast supernatant or non-viable yeast also did not show any stabilising effects, suggesting that physical contact and/or interaction between viable W. saturnus and B. lactis plays an important role in sustaining the viability of the probiotic. W. saturnus NCYC 22 could increase the survival of B. lactis in bifidus milk under ambient temperature regardless of the initial concentration of yeast cells inoculated due to yeast growth. This study demonstrated the viability enhancing effect of viable W. saturnus NCYC 22 on B. lactis HN019, which could help towards extending the shelf-life of dairy beverages containing probiotic bifidobacteria.

Influence ofSaccharomyces cerevisiaeandWilliopsis saturnusvar.Mrakiion mango wine characteristics

Saccharomyces cerevisiae MERIT.ferm was used as mono- and mixed-cultures with Williopsis saturnus var. mrakii NCYC500 in mango wine fermentation. A ratio of 1:1000 (Saccharomyces:Williopsis) was chosen for mixed-culture fermentation to enable longer persistence of the latter. The monoculture of S. cerevisiae and mixed-culture was able to ferment to dryness with 7.0% and 7.7% ethanol, respectively. The monoculture of W. mrakii produced 1.45% ethanol. The mango wines fermented by S. cerevisiae alone and the mixed-culture were more yeasty and winey, which reflected their higher amounts of fusel alcohols, ethyl esters and medium-chain fatty acids. The mango wine fermented by W. mrakii alone was much less alcoholic, but fruitier, sweeter, which corresponded to its higher levels of acetate esters.

Cider fermentation with three Williopsis saturnus yeast strains and volatile changes

Williopsis saturnus var. subsufficiens NCYC 2728, W. saturnus var. saturnus NCYC 22 and W. saturnus var. mrakii NCYC 500 were used to carry out cider fermentation to assess their impact on the volatile composition of cider. The changes of yeast cell population, °Brix and pH were similar among the three yeasts. Strain NCYC 500 grew best, with the highest cell population of 1.14 × 108 CFU ml−1, followed by strains NCYC 2728 and NCYC 22 (8 × 107 CFU ml−1 and 3.19 × 107 CFU ml−1 respectively). Esters were the most abundant volatiles produced, followed by alcohols. Among the esters, ethyl acetate, 2-phenylethyl acetate, isoamyl acetate, cis-3-hexenyl acetate and hexyl acetate were the major volatiles. The major alcohols were ethanol, isoamyl alcohol, 2-phenylethyl alcohol and isobutyl alcohol. The three Williopsis yeasts transformed volatile compounds during cider fermentation with significant variations in terms of volatile production and degradation. This study implied that fermentation with Williopsis yeasts could result in cider with a more complex yet fruity aroma.

Fermentation of three varieties of mango juices with a mixture of Saccharomyces cerevisiae and Williopsis saturnus var. mrakii

This study was carried out to ascertain the behavior and fermentation performance of mixed yeasts in mango juices of three varieties. Saccharomyces cerevisiae MERIT.ferm and Williopsis saturnus var. mrakii NCYC500 at a ratio of 1:1000 were simultaneously inoculated into juices of three mango (Mangifera indica L.) varieties (R2E2, Harum Manis and Nam Doc Mai). Both yeasts grew well in all juices and there was no early growth arrest of either yeast, but there was late death of W. saturnus var. mrakii NCYC500 in the Nam Doc Mai juice. Fructose, glucose and sucrose were consumed to trace levels in all juices. Changes in citric, tartaric, malic, acetic and succinic acids varied with mango varieties. While the changes of major volatiles were similar in all varieties, there were significant varietal differences in the volatile composition of the resultant mango wines. The volatiles, especially most of the terpenes, of the juices decreased drastically and new volatiles such as β-citronellol were formed. R2E2 wine had more fruity, sweet and creamy notes, and retained more of its original character due to a higher retention of ketones/lactones. Harum Manis wine had the lowest aroma intensity with more green and terpenic notes associated with higher levels of residual terpenes than the other two varieties. Nam Doc Mai wine possessed the highest aroma intensity with winey, yeasty, fruity and floral notes attributed to higher amounts of alcohols, acetate esters and ethyl esters. These findings may help develop different styles of mango wine.

Impact of two Williopsis yeast strains on the volatile composition of mango wine

SummaryThe aim of the research was to study the volatile composition of mango wine fermented with two Williopsis yeast strains: Williopsis saturnus var. mrakii NCYC500 and W. staurnus var. suaveolens NCYC2586. Thirty terpenoids, twenty‐six esters, ten alcohols, nine acids, seven aldehydes and ketones, two ethers, two phenols and one sulphur compound were identified in the mango wine fermented with strain NCYC500, while twenty‐seven terpenoids, thirty esters, eleven alcohols, eight acids, eight aldehydes and ketones, three ethers, two phenols, one sulphur compound and one furan were detected in the mango wine fermented with the strain NCYC2586. The kinetic changes, final concentrations and odour activity values of major volatiles were compared between the two Williopsis yeast strains and also with other yeast reported in the literature. The results showed that Williopsis yeast strains NCYC500 and NCYC2586 were high producers of acetic acid and acetate esters, but low producers of medium‐ to long‐chain fatty acids and their corresponding ethyl esters. Unlike mango wine fermented with Saccharomyces cerevisiae, most terpenoids derived from mango juice were retained in the resultant mango wine fermented with the two Williopsis yeast strains, suggesting the mango wine could retain the aromatic hints of fresh mango.

Effects of sequentially inoculated Williopsis saturnus and Saccharomyces cerevisiae on volatile profiles of papaya wine

The effects of sequential inoculation of yeasts Williopsis saturnus var. mrakii NCYC2251 and Saccharomyces cerevisiae var. bayanus R2 on the volatile profiles of papaya wine were investigated at an inoculum ratio of 1000 (W. saturnus) to 1 (S. cerevisiae). Inoculation of S. cerevisiae after seven days' fermentation with W. saturnus produced papaya wine with more acetate esters and fruitiness than the control (simultaneous inoculation). However, inoculation of W. saturnus after two days' fermentation with S. cerevisiae resulted in most of the volatile composition being comparable to the control, except for the enhanced amount of ethyl esters. The first inoculated yeast dominated the fermentation. The study suggests that sequential inoculation of non-Saccharomyces and Saccharomyces yeasts at a certain inoculum ratio may be a valuable tool to manipulate yeast succession and to modulate the volatile profiles and organoleptic properties of papaya wine.

FORMATION OF AROMA COMPOUNDS DURING LONGAN JUICE FERMENTATION BY WILLIOPSIS SATURNUS VAR. SATURNUS WITH THE ADDITION OF SELECTED AMINO ACIDS

ABSTRACT Longan (Dimocarpus longan Lour.) is a type of tropical fruit. This study investigated the impact of L-leucine and L-phenylalanine on the volatile profiles of longan wine fermented with a non-Saccharomyces yeast Williopsis saturnus ssp. saturnus CBS254 with a view to enhancing longan wine aroma. The results revealed the ability of this yeast to enhance isoamyl alcohol and its ester isoamyl acetate (banana-like aroma), and 2-phenylethanol and its ester 2-phenylethyl acetate (rose-like aroma) with the addition of L-leucine and L-phenylalanine, respectively. The increased production of the targeted acetate esters appeared to be at the expense of other acetate esters except for methyl acetate, whereas the effects on the biotransformation of other volatiles were minimal. Therefore, these findings suggest that the combination(s) of an amino acid and yeast can be employed as a tool to manipulate the level of the targeted aroma compounds so as to impart a specific aroma or to add flavor complexity to longan wine. PRACTICAL APPLICATIONS Tropical fruits such as longan are often in oversupply during the peak season and some are wasted because of lack of adequate processing technologies. Thus, there is a need to add value to longan fruit via processing. Although drying as a form of processing is commonly applied to longan fruit, fermentation is not widely practiced to process and preserve this fruit because of lack of research and information. Longan wine fermentation using the conventional grape wine fermentation technology results in longan wine with inferior flavor. The aim of this study is to investigate the fermentation of longan juice using a non-Saccharomyces yeast Williopsis saturnus var. saturnus with addition of L-leucine and L-phenylalanine so as to modulate the formation of aroma compounds.

Effect of fusel oil addition on volatile compounds in papaya wine fermented with Williopsis saturnus var. mrakii NCYC 2251

The impact of fusel oil addition on volatile compounds formation in papaya wine fermented with yeast Williopsis saturnus var. mrakii NCYC2251 was studied with a view to enhancing papaya wine aroma production. Time-course papaya juice fermentations were carried out using W. saturnus var. mrakii NCYC2251 with fusel oil added (0, 0.1 and 0.5% v/v). Fermentation characteristics in terms of yeast growth, Brix and pH changes were similar for all fermentations except for those added with 0.5% (v/v) fusel oil. The addition of 0.5% (v/v) fusel oil inhibited yeast growth. A wide range of volatile compounds were produced during fermentation including acids, alcohols, esters and aldehydes with esters being the most abundant volatile compounds produced. The addition of 0.1% (v/v) fusel oil reduced the production of undesirable volatiles such as ethyl acetate and acetic acid, while increasing the desirable volatiles production such as ethanol and acetate esters. This study suggests that papaya juice fermentation with W. saturnus var mrakii NCYC 2251 together with a low concentration of added fusel oil can be another means of modulating papaya wine aroma compound formation.

Growth and fermentation kinetics of a mixed culture of Saccharomyces cerevisiae var. bayanus and Williopsis saturnus var. saturnus at different ratios in longan juice (Dimocarpus longan Lour.)

Summary Cofermentation of longan juice by mixed cultures of Saccharomyces cerevisiae var. bayanus EC-1118 and Williopsis saturnus var. saturnus CBS254 at two inoculation ratios (EC-1118:CBS254 = 1:100 and 1:1000 cfu mL−1) was performed to ascertain their impact on longan wine aroma compound formation. The results showed improved aroma compound profiles in the longan wine fermented with mixed yeasts in comparison with the longan wines fermented with single yeasts in terms of increased production of acetate esters, fatty acid ethyl esters, alcohols and carboxylic acids. The impact of cofermentation on longan wine aroma formation was affected by the ratio of S. cerevisiae EC-1118 to W. saturnus CBS254 with 1:100 cfu mL−1 being more effective. This research suggests that the inoculation ratio of mixed yeasts may be used as an effective means of manipulating longan wine aroma.

Williopsis saturnus yeast killer toxin does not kill Streptococcus pneumoniae

Streptococcus pneumoniae is an important human bacterial pathogen, and the increase in antibiotic resistance demands the development of new antimicrobial compounds. Several reports have suggested that yeast killer toxins show activity against bacteria and we therefore investigated the activity of K9 killer toxin from the yeast Williopsis saturnus var. mrakii NCYC 500 against S. pneumoniae. However, no inhibition of bacterial growth was observed with concentrated K9 preparations in agar diffusion assays and in liquid culture. Although cell morphology was slightly affected by K9 treatment, no effect on cellular viability was detectable, and K9 had no stimulatory effect on cell lysis induced by β-lactams or Triton X-100. This indicated that K9 did not contribute to cell wall damage. Moreover, flow cytometry was used as a sensitive assessment of integrity of cells exposed to killer toxin. No significant damage of S. pneumoniae cells was evident, although minor changes in fluorescence suggested that K9 killer toxin may interact with bacterial surface components.