Effects of Chromium Brewer’s Yeast Supplementation on Body Mass,Blood Carbohydrates,and Lipids and Minerals in Type 2 Diabetic Patients

Chromium(III) is considered as an essential element for carbohydrate and lipid metabolism. The aim of this clinical study was to evaluate the efficacy of Cr brewer’s yeast supplementation on body mass, carbohydrate, lipids and mineral indices in type 2 diabetic patients. Twenty adult type 2 diabetic subjects (11 males and 9 females aged 37–63) were supplemented with Cr brewer’s yeast in dosages of 500 μg Cr/person/day or placebo for 8 weeks in a double-blind, placebo-controlled crossover design. It was found that supplemental Cr did not affect body mass, blood lipid profile, resistin levels, and the serum and hair Zn, Fe, and Cu levels, but increased serum Cr (by 116%) and hair Cr (by 20.6%) concentrations and improved some blood carbohydrate indices (significant increase in the β cell function index by 18.8%) in type 2 diabetic patients. In conclusion, Cr brewer’s yeast has a weak hypoglycemic potential, but does not affect body mass, blood biochemical profile, and microelement levels in type 2 diabetic subjects.     

Genetic improvement of brewer’s yeast: current state, perspectives and limits

Brewer’s yeast strain optimisation may lead to a more efficient beer production process, better final quality or healthier beer. However, brewer’s yeast genetic improvement is very challenging, especially true when it comes to lager brewer’s yeast (Saccharomyces pastorianus) which contributes to 90% of the total beer market. This yeast is a genetic hybrid and allopolyploid. While early studies applying traditional genetic approaches encountered many problems, the development of rational metabolic engineering strategies successfully introduced many desired properties into brewer’s yeast. Recently, the first genome sequence of a lager brewer’s strain became available. This has opened the door for applying advanced omics technologies and facilitating inverse metabolic engineering strategies. The latter approach takes advantage of natural diversity and aims at identifying and transferring the crucial genetic information for an interesting phenotype. In this way, strains can be optimised by introducing “natural” mutations. However, even when it comes to self-cloned strains, severe concerns about genetically modified organisms used in the food and beverage industry are still a major hurdle for any commercialisation. Therefore, research efforts will aim at developing new sophisticated screening methods for the isolation of natural mutants with the desired properties which are based on the knowledge of genotype–phenotype linkage.     

Bioconversion of ethyl 4-chloro-3-oxobutanoate by permeabilized fresh brewer’s yeast cells in the presence of allyl bromide

Ethyl(R)-4-chloro-3-hydroxybutanoate ((R)-CHBE) are obtained by cetyltrimetylammonium bromide (CTAB) permeabilized fresh brewer’s yeast whole cells bioconversion of ethyl 4-chloro-3-oxobutanoate (COBE ) in the presence of allyl bromide. The results showed that the activities of alcohol dehydrogenase (ADH) and glucose-6-phosphate dehydrogenase (G6PDH) in CTAB permeabilized brewer’s yeast cells increased 525 and 7.9-fold, respectively, compared with that in the nonpermeabilized cells and had high enantioselectivity to convert COBE to (R)-CHBE. As one of co-substrates, glucose-6-phosphate was preprepared using glucose phosphorylation by hexokinase-catalyzed of CTAB permeabilized brewer’s yeast cells. In a two phase reaction system with n-butyl acetate as organic solvent and with 2-propanol and glucose-6-phosphate as co-substrates, the highest (R)-CHBE concentration of 447 mM was obtained with 110–130 g/l of the CTAB permeabilized cells at optimized pH, temperature, feeding rate and the shake speed of 125 r/min. The yield and enantiomeric excess (ee) of (R)-CHBE reached 99.5 and 99%, respectively, within 6 h.     

Flocculation gene variability in industrial brewer’s yeast strains

The brewer’s yeast genome encodes a ‘Flo’ flocculin family responsible for flocculation. Controlled floc formation or flocculation at the end of fermentation is of great importance in the brewing industry since it is a cost-effective and environmental-friendly technique to separate yeast cells from the final beer. FLO genes have the notable capacity to evolve and diverge many times faster than other genes. In actual practice, this genetic variability may directly alter the flocculin structure, which in turn may affect the flocculation onset and/or strength in an uncontrolled manner. Here, 16 ale and lager yeast strains from different breweries, one laboratory Saccharomyces cerevisiae and one reference Saccharomyces pastorianus strain, with divergent flocculation strengths, were selected and screened for characteristic FLO gene sequences. Most of the strains could be distinguished by a typical pattern of these FLO gene markers. The FLO1 and FLO10 markers were only present in five out of the 18 yeast strains, while the FLO9 marker was ubiquitous in all the tested strains. Surprisingly, three strongly flocculating ale yeast strains in this screening also share a typical ‘lager’ yeast FLO gene marker. Further analysis revealed that a complete Lg-FLO1 allele was present in these ale yeasts. Taken together, this explicit genetic variation between flocculation genes hampers attempts to understand and control the flocculation behavior in industrial brewer’s yeasts.     

Influence of growth phase and zeolite clinoptilolite on the concentration of sphingoid bases in Saccharomyces uvarum brewer’s yeast

Sphingolipids having a long-chain sphingoid base backbone are primarily located in the yeast’s plasma membrane. They are found in various types of foods, and although they are not essential food ingredients, they play an important role as bioactive molecules in preventing certain human diseases. Today, due to its high nutritional value, brewer’s yeast is increasingly being used in the food and pharmaceutical industry. The aim of this study was to evaluate the potential of S. uvarum, a by-product of the brewing industry, as an economically feasible source of sphingolipids. For that purpose, the growth phase dependence on sphingolipid production in S. uvarum as well as the effect of zeolite addition to the growth medium was investigated. The experiments were designed to explore the dependence of growth phase on sphingolipids metabolism, by comparing initial (starter) culture of brewer’s yeast (laboratory propagated, designated as zero yeast generation, serving here as control), and surplus brewer’s yeast (a residue produced after 5 successive beer fermentations), by-product of beer fermentation, with and without the addition of zeolite. HPLC analysis of individual molecular species of sphingoid bases obtained by acid hydrolysis of complex sphingolipids from S. uvarum yeast produced the following results: about 65% of total sphingoid bases represents C18 phytosphingosine, about 32% represents unknown long-chain base, and about 1.5–2% represents C18 DL-erythro-sphinganine. In the case of C18 phytosphingosine, production was about 11.5-fold higher during exponential phase compared with the other growth phases. For C18 DL-erythro-sphinganine, production was highest during the lag and acceleration phase of growth. In most cases, zeolite addition (1%) to the growth medium resulted in an increase up to 2.5-fold in the sphingoid bases level.     

Physiological characterization of brewer’s yeast in high-gravity beer fermentations with glucose or maltose syrups as adjuncts

High-gravity brewing, which can decrease production costs by increasing brewery yields, has become an attractive alternative to traditional brewing methods. However, as higher sugar concentration is required, the yeast is exposed to various stresses during fermentation. We evaluated the influence of high-gravity brewing on the fermentation performance of the brewer’s yeast under model brewing conditions. The lager brewer’s strain Weihenstephan 34/70 strain was characterized at three different gravities by adding either glucose or maltose syrups to the basic wort. We observed that increased gravity resulted in a lower specific growth rate, a longer lag phase before initiation of ethanol production, incomplete sugar utilization, and an increase in the concentrations of ethyl acetate and isoamyl acetate in the final beer. Increasing the gravity by adding maltose syrup as opposed to glucose syrup resulted in more balanced fermentation performance in terms of higher cell numbers, respectively, higher wort fermentability and a more favorable flavor profile of the final beer. Our study underlines the effects of the various stress factors on brewer’s yeast metabolism and the influence of the type of sugar syrups on the fermentation performance and the flavor profile of the final beer.     

Effects of industrial storage on the bioreduction capacity of brewer’s yeast

The effects of industrial storage on the changes of the cell viability and the activities of intracellular alcohol dehydrogenase (ADH) and glucose-6-phosphate dehydrogenase (G6PDH) in brewer’s yeast, and the corresponding capacity for the bioconversion of ethyl-3-oxobutanoate (EOB) to ethyl (S)-3-hydroxybutanoate ((S)-EHB), were investigated. The viability of fresh brewer’s yeast cells stored in industrial circulating cooling water at 1–2°C showed 4 and 15% drop after the storage of 7 and 15 days, respectively, after which cells died rapidly. The pretreatment of the stored brewer’s yeast cells by washing and screening significantly enhanced cell viability during industrial storage. The intracellular levels of ADH and G6PDH after permeabilization of these stored cells with cetyltrimetylammonium bromide (CTAB) were much higher, which showed only slight decrease within 2 weeks during the industrial storage. When the stored cells after the permeabilization treatment was used as the biocatalyst at 90–120 g/L, EOB was converted almost completely into enantiopure (S)-EHB with an enantiomeric excess (ee) more than 99% and a yield of over 96%, by fed-batch bioconversion of 560 mM EOB within 6 h. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Biosorption of heavy metals from acid mine drainage onto biopolymers (chitin and α (1,3) β-D-glucan) from industrial biowaste exhausted brewer’s yeasts (Saccharomyces cerevisiae L.)

A biosorption process has been developed for the bioremediation of heavy metal-contaminated acid drainages from Merladet and Faith open-cast mines, located in western Spain. The process is based on the physico-chemical properties for the adsorption, ion exchange, and complexation of metal ions by biopolymers (chitin and α (1,3) β-D-glucan) from industrial biowaste exhausted brewer’s yeast (Saccharomyces cerevisiae L.). Firstly, the chemical composition (U, Mn, Al, Fe, Cu, Zn, and Ni) and the physico-chemical and ecological states of these acid mine drainages were characterised. Furthermore, the selectivity for Zn, Cu, Mn, Ni, and Al the first order kinetics and the performance of the metals biosorption process by exhausted brewer’s yeast were evaluated with polluted acid synthetic waters and mine drainages. The biosorption equilibria were reached in 10 ∼ 15 min following Langmuir type isotherms with higher affinity constants for metal-biosorbent binding for synthetic waters than for acid mine drainages. The efficiency of the process with real water samples was markedly lower for the case of Mn, and zero for Zn and Al. An antagonistic interference on the biosorption of a metal due to the presence of other metals is proposed. Finally, the ecotoxicity of the acid mine drainage was removed when it was incubated with brewer’s yeast trapped in polyurethane foam.     

Maltotriose transport and utilization in Baker’s and Brewer’s yeast

Maltotriose is metabolized by baker’s and brewer’s yeast only oxidatively, with a respiratory quotient of 1.0, the being, depending on the strain used, 0–11, as compared with of 6–42μL CO₂ per h per mg dry substance. The transport appeared to proceed by facilitated diffusion (no effects of NaF, iodoacetamide and 3-chlorophenylhydrazonomalononitrile) with a K_T of more than 50mm and was inhibited by maltose > maltotriose > methyl-α-D-glucoside > maltotetraose >D-fruetose >D-glucose. The transport was present constitutively in bothSaccharomyces cerevisiae (baker’s yeast) and inS. uvarum (brewer’s yeast) and it was not significantly stimulated by preincubation with glucose or maltose. The pH optimum was 4.5–5.5, the temperature dependence yielded an activation energy of 26 kJ/mol.     

Extra-cellular chromate-reducing activity of the yeast cultures

This paper reports on the experimental data supporting an essential role of extra-cellular reduction in chromate detoxification by baker’s and non-conventional yeasts. A decrease of chromate content in the yeast culture coincides with an increase of Cr(III) content in extra-cellular liquid. At these conditions, cell-bound chromium level was insignificant and a dominant part of extra-cellular Cr(III) species was detected in the reaction with chromazurol S only after mineralization of the cell-free samples. This phenomenon of chromium “disappearance” can be explained by the formation of Cr(III) stable complexes with extra-cellular yeast-secreted components which are “inaccessible” in the reaction with chromazurol S without mineralization. It was shown that increasing sucrose concentration in a growth medium resulted in an increase of chromate reduction. A strong inhibition of chromate reduction by 0.25 mM sodium azide, a respiration inhibitor and a protonophore, testifies that extra-cellular chromate detoxification depends on energetic status of the yeast cells. It was shown that Cr(III)-biochelates produced in extra-cellular medium are of a different chemical nature and can be separated into at least two components by ion-exchange chromatography on anionit Dowex 1x10. A total yield of the isolated Cr(III)-biocomplexes is approximately 65 % (from initial level of chromate) with a relative molar ratio 8:5.     

Kinetic and Morphological Observations on the Yeast Phase of Histoplasma capsulatum During Protoplast Formation

Protoplast formation by Histoplasma capsulatum yeasts using high concentrations of MgSO(4) occurs either by lysis of the bud or lysis of the entire cell wall. Both mechanisms may also occur simultaneously. Neither the protoplast emerging through a hole in the cell wall nor the freshly released protoplast has a recognizable cell wall or the remnant of such. The protoplast contains all the organelles of the normal cell except for mesosomes. During protoplast formation the nucleus increases in size and produces several nuclear masses by the invaginations of the internal layer of the nuclear membrane. All these nuclear masses are surrounded by the external layer of the nuclear membrane. Several nuclei with a normal nuclear membrane are formed later.     

Enzymatic synthesis of glutathione using yeast cells in two-stage reaction

In the present study, permeated yeast cells were used as the catalyst to synthesize glutathione. When waste cells of brewer’s yeast were incubated with the three precursor amino acids and glucose for 36 h, 899 mg/L of glutathione were produced. To release the feedback inhibition of γ-glutamylcysteine synthetase caused by glutathione, two-stage reaction was adopted. In the first stage, glycine was omitted from the reaction mixture and only γ-glutamylcysteine was formed. Glycine was then added in the second stage, and 1,569 mg/L of glutathione were produced. The conditions of the two-stage reaction were optimized using Plackett–Burman design and response surface methodology. Under the optimized condition, commercially available baker’s yeast produced 3,440 mg/L of glutathione in 30 h, and most of the produced glutathione was in the medium. The two-stage reaction could effectively reduce the feedback inhibition caused by glutathione, but degradation of glutathione was significant.     

糖蜜发酵培养富铬酵母

筛选对铬元素吸收较好的产朊园酵母(Torulopsisutilis)为实验菌株,根据铬的耐受量实验,确定糖蜜培养基铬的添加量,研究富铬酵母培养最佳工艺条件,探讨富铬酵母的应用。发酵产品富铬酵母铬的含量7388mgkg,蛋白质含量4874%(ww),得率30%(wv)。     

A comparative study of submicroscopic structures of protoplasts of various yeast species

A submicroscopic structure was studied of protoplasts of five different yeast species multiplying by budding, formation of cross septum and by a division typical for apiculate yeasts. The protoplasts retain their species specificity. Most considerable changes typical for the conversion of a cell to protoplast are found in membrane cell systems. The reduction of membranes of the endoplasmic reticulum is particularly striking. Both membrane units are frequently separated from each other by lenticular pseudovacuoles. Mitochondria in protoplasts are swollen and their number is reduced approximately two-fold. Defects are often observed in a nuclear membrane. The perinuclear space is usually extended by lenticular pseudovacuoles. A large number of vacuoles is observed in the basic protoplast cytoplasm. The surface of the protoplasts of all species studied is formed only by a cytoplasmic membrane. A partially digested original cell wall often adheres to protoplasts ofSchizosaccharomyces pombe.     

Influence of stressful fermentation conditions on neutral lipids of a Saccharomyces cerevisiae brewing strain

The neutral lipid fraction of the aerobically grown starter yeast culture of a Saccharomyces cerevisiae brewing strain, and three-first recycled yeast generations exposed to multiple stress factors during beer fermentation was studied. No pronounced changes in the cellular neutral lipid content between the non-stressed starter and stressed recycled cells were found. However, it was found that recycled yeast generations modulate their neutral lipid composition during fermentation. The ergosterol content was increased at the expense of steryl esters (SEs) and squalene, which resulted in a higher ergosterol/SEs molar ratio and a slightly higher ergosterol/squalene molar ratio. In addition, the proportion of unsaturated fatty acids, mainly palmitoleic acid increased in the neutral lipid fraction of the stressed recycled yeast generations. These results suggest that some specific neutral lipid species and fatty acids stored in the neutral lipid fraction are involved in the adaptive response of the brewer’s yeast to stressful fermentation conditions. The striking finding was a high squalene content in the neutral lipid fraction of both the starter yeast culture and recycled yeast generations (22.4 vs. 19–20%, respectively), implying a possible biotechnological exploitation of this biologically active molecule from the yeast biomass.     

富铬酵母的理化性质和氨基酸分析

用２００～３００ｎｍ的波长范围对富铬酵母及普通酵母的溶液进行紫外扫描,发现在λ_(２６０ｎｍ)处有一特征紫外吸收峰,富铬酵母细胞的铬含量与其吸收峰的光密度呈线性关系;在不同的温度和ｐＨ值条件下,通过紫外吸收峰的测定,富铬酵母溶液在酸性条件下稳定,在碱性条件下不稳定。溶液的λ_(２６０ｎｍ)紫外吸收峰随着温度的上升而升高。从氨基酸含量分析结果看,富铬酵母的谷氨酸、甘氨酸、组氨酸、丙氨酸和赖氨酸含量高于普通酵母,但其他氨基酸含量比普通酵母低。     

An investigation by ion-exchange chromatography of a chromium,amino acid and nicotinic acid mixture

The mixture of chromium, nicotinic acid and the amino acids glycine, glutamic acid and cysteine which stimulates the rate of CO₂ production in a yeast bioassay system was subjected to the separation scheme based on ion-exchange chromatography which has been used to separate the chromium- containing fractions in brewer's yeast, [S.J. Haylock, P.D. Buckley and L.F. Blackwell, J. Inorg. Biochem., 18, 195 (1983)]. Four chromium-containing fractions (C2 to C5) were obtained by salt gradients and two further fractions (G1 and G2) were obtained using a pH gradient. All were amino acid-containing complexes of chromium and all except C5 also contained nicotinic acid. However, none of the isolated chromium fractions showed any activity in a yeast bioassay. On the basis of previous work, the activity of the original mixture was attributed to the presence of an oxygen-coordinated trans chromium(III)-dinicotinate complex. Biologically- inactive chromium complexes such as Cr(glu)₂(H₂O)⁺₂ and Cr(gly)₂(H₂O)⁺₂ after elution by ammonium hydroxide from Dowex 50W-X12 cation- exchange columns, stimulated the rate of CO₂ production in the yeast bioassay. Elution with other bases, such as lithium hydroxide, potassium hydroxide and sodium hydroxide led to inactive fractions in all cases. A warning is therefore given that the use of ammonium hydroxide-elution of ion-exchange columns to isolate glucose tolerance factor fractions from biological samples (such as brewer's yeast) can lead to active fractions which do not relate to the native material.     

Structural and immunological studies on the protoplast membrane of the yeast Candida utilis

Cell membranes of the yeast Candida utilis isolated by lysis of protoplasts have been shown to be lipoprotein in nature. Electron microscopy shows that Mg⁺⁺ is responsible for maintaining the integrity of the membrane. A close serological relationship was found between membranes and cell walls isolated from the yeast. This relationship was exhibited not only by membranes obtained by strepzyme treatment but also by those obtained from the action of helicase enzyme. No such relationship existed between membranes and whole cells. Related data have been obtained by treatment of yeasts with different digestive enzymes. All of the results suggest that the protoplast membrane possesses traces of structural cell wall material. This material is detectable by serological tests, but not by electron microscopy.     

Beneficial effects of chromium in people with type 2 diabetes, and urinary chromium response to glucose load as a possible indicator of status

No reliable method for the estimation of chromium (Cr) status is available yet. The aim of this study is to investigate the possibility of using urinary Cr response to glucose load as an indicator of Cr status. Seventy-eight non-insulin-dependent diabetes mellitus patients were divided randomly into two groups and given Cr supplements as brewer’s yeast and CrCl₃ sequentially with placebo in between, in a double-blind, crossover design of four stages, each lasting 8 wk. At the beginning and end of each stage, subjects were weighed, their dietary data and drug dosage recorded, and blood and urine samples collected for analysis of glucose and urinary chromium (fasting and 2 h post-75-g glucose load) and fructosamine. The mean urinary Cr after the glucose load was significantly higher than the fasting mean at zero time (p<0.01). However, only 52 of the patients showed an obvious increase; the others showed a slight decrease or no change. Both supplements caused a significant increase in the means of urinary Cr and a significant decrease in the means of glucose and fructosamine. Only those subjects responding to Cr supplement by improved glucose control showed an increase in post-glucose-load urinary Cr over fasting level, after the supplement but not at zero time. Therefore, it was concluded that urinary Cr response to glucose load could be used as an indicator of Cr status.     

Effect of <Emphasis Type="Italic">Agave tequilana</Emphasis> juice on cell wall polysaccharides of three <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> strains from different origins

In this study, a characterization of cell wall polysaccharide composition of three yeasts involved in the production of agave distilled beverages was performed. The three yeast strains were isolated from different media (tequila, mezcal and bakery) and were evaluated for the β(1,3)-glucanase lytic activity and the β-glucan/mannan ratio during the fermentation of Agave tequilana juice and in YPD media (control). Fermentations were performed in shake flasks with 30 g l⁻¹ sugar concentration of A. tequilana juice and with the control YPD using 30 g l⁻¹ of glucose. The three yeasts strains showed different levels of β-glucan and mannan when they were grown in A. tequilana juice in comparison to the YPD media. The maximum rate of cell wall lyses was 50% lower in fermentations with A. tequilana juice for yeasts isolated from tequila and mezcal than compared to the bakery yeast.