Dry Yeast Biomass Research Articles

Bioprocess Optimization by Taguchi Design and Response Surface Analysis for Obtaining Active Yeast Used in Vinification

This study presents the behavior of the identified yeast strain S. cerevisiae, isolated from Busuioacă de Bohotin grapes from the Pietroasa winery, during the process of fermentation to obtain dry active yeast biomass for the winemaking process. In this respect, we promoted an optimization strategy for obtaining active dry yeast biomass. The cultivation conditions for micropilot fermentation (temperature, pH, carbon source, and nitrogen source) were selected and designed according to a Taguchi design with four factors and three levels. Reproducibility testing was conducted under specific fermentation parameters: temperature (32 °C), pH (4.5), carbon source (12%), and nitrogen source (0.7%). Following the optimization process, two combinations of cultivation parameters were selected, and one of them, based on the results, was selected for further analysis. Quantitative data were obtained, showing dry yeast biomass (DCW) at 1.39 g/100 mL and protein content at 45.57%. The active yeast was then used in the winemaking process for Tămâioasă Românească and Busuioacă de Bohotin varieties at Pietroasa winery for validation. This optimization aims to facilitate easy and rapid production of fresh wine yeast tailored to the local winemaking practices of Pietroasa winery, with real application potential in other viticultural areas, aligning with the terroir concept.

Fungistatic Effect of Phthalide Lactones on Rhodotorula mucilaginosa.

Currently, there is an increasing number of cases of fungal infections caused by opportunistic strains of the yeast Rhodotorula mucilaginosa, mainly in immunocompromised patients during hospitalization. The excessive use of antibiotics and azole compounds increases the risk of resistance to microorganisms. A new alternative to these drugs may be synthetic phthalide lactones with a structure identical to or similar to the natural ones found in celery plants, which show low toxicity and relatively high fungistatic activity. In the present study, the fungistatic activity of seven phthalide lactones was determined against R. mucilaginosa IHEM 18459. We showed that 3-n-butylidenephthalide, the most potent compound selected in the microdilution test, caused a dose-dependent decrease in dry yeast biomass. Phthalide accumulated in yeast cells and contributed to an increase in reactive oxygen species content. The synergistic effect of fluconazole resulted in a reduction in the azole concentration required for yeast inhibition. We observed changes in the color of the yeast cultures; thus, we conducted experiments to prove that the carotenoid profile was altered. The addition of lactones also triggered a decline in fatty acid methyl esters.

Nitrogen recovery from low-value biogenic feedstocks via steam gasification to methylotrophic yeast biomass.

Carbon and nitrogen are crucial elements for life and must be efficiently regenerated in a circular economy. Biomass streams at the end of their useful life, such as sewage sludge, are difficult to recycle even though they contain organic carbon and nitrogen components. Gasification is an emerging technology to utilize such challenging waste streams and produce syngas that can be further processed into, e.g., Fischer-Tropsch fuels, methane, or methanol. Here, the objective is to investigate if nitrogen can be recovered from product gas cleaning in a dual fluidized bed (DFB) after gasification of softwood pellets to form yeast biomass. Yeast biomass is a protein-rich product, which can be used for food and feed applications. An aqueous solution containing ammonium at a concentration of 66mM was obtained and by adding other nutrients it enables the growth of the methylotrophic yeast Komagataella phaffii to form 6.2g.L-1 dry yeast biomass in 3days. To further integrate the process, it is discussed how methanol can be obtained from syngas by chemical catalysis, which is used as a carbon source for the yeast culture. Furthermore, different gas compositions derived from the gasification of biogenic feedstocks including sewage sludge, bark, and chicken manure are evaluated for their ability to yield methanol and yeast biomass. The different feedstocks are compared based on their potential to yield methanol and ammonia, which are required for the generation of yeast biomass. It was found that the gasification of bark and chicken manure yields a balanced carbon and nitrogen source for the formation of yeast biomass. Overall, a novel integrated process concept based on renewable, biogenic feedstocks is proposed connecting gasification with methanol synthesis to enable the formation of protein-rich yeast biomass.

The microbial production of kynurenic acid using Yarrowia lipolytica yeast growing on crude glycerol and soybean molasses.

Yarrowia lipolytica yeast are able to produce kynurenic acid—a very valuable compound acting as a neuroprotective and antioxidant agent in humans. The recent data proved the existence of the kynurenine biosynthesis pathway in this yeast cells. Due to this fact, the aim of this work was to enhance kynurenic acid production using crude glycerol and soybean molasses as cheap and renewable carbon and nitrogen sources. The obtained results showed that Y. lipolytica GUT1 mutants are able to produce kynurenic acid in higher concentrations (from 4.5 mg dm−3 to 14.1 mg dm−3) than the parental strain (3.6 mg dm−3) in the supernatant in a medium with crude glycerol. Moreover, the addition of soybean molasses increased kynurenic acid production by using wild type and transformant strains. The A-101.1.31 GUT1/1 mutant strain produced 17.7 mg dm−3 of kynurenic acid in the supernatant during 150 h of the process and 576.7 mg kg−1 of kynurenic acid in dry yeast biomass. The presented work proves the great potential of microbial kynurenic acid production using waste feedstock. Yeast biomass obtained in this work is rich in protein, with a low content of lipid, and can be a healthy ingredient of animal and human diet.

Optimization of the Fermentation Conditions for Brewing Yeast Biomass Production Using the Response Surface Methodology and Taguchi Technique

Yeast (including brewing yeast) and yeast-based preparations derived from bioprocesses or agroindustrial byproducts represent valuable feed additives and ingredients for ruminants. The optimization of brewing yeast biotechnological processing through fermentation mediated by the brewing yeast strain Saccharomyces pastorianus ssp. carlsbergensis W34/70 was investigated. The cultivation conditions (temperature, pH, carbon source, and nitrogen source) were selected and designed according to a Taguchi fractional experimental plan, with four factors on three levels, and their influence on the evolution of the bioprocess of obtaining the brewing yeast biomass was evaluated. The dependent variables were the yeast biomass amount in wet form, yeast biomass amount in dried form after lyophilization, dried yeast biomass wettability assayed through the contact angle (CA), protein content (PC), and dry matter content (DS). The effects that the experimental conditions had on the system responses were visualized in tridimensional space using the response surface methodology, and the combination of biotechnological parameters that ensured process quality and robustness was then determined using the Taguchi technique through its performance indicator, i.e., the signal-to-noise ratio. By optimizing the biotechnological parameters, this study provides a valuable contribution in the area of brewing yeast biomass processing, with the aim of producing probiotic yeast for ruminant nutrition.

Bioconversion of sago processing wastewater into biodiesel: Optimization of lipid production by an oleaginous yeast,\xa0Candida tropicalis\xa0ASY2 and its transesterification\xa0process using response surface methodology

BackgroundBiodiesel is an eco-friendly and renewable energy source and a valuable substitute for petro-diesel. Sago processing wastewater (SWW), a by-product of the cassava processing industry, has starch content ranging from 4 to 7 g L–1 and serves as an outstanding source for producing microbial lipids by the oleaginous microorganisms. In the present study, Candida tropicalis ASY2 was employed to optimize single-cell oil (SCO) production using SWW and subsequent transesterification by response surface methodology. Variables such as starch content, yeast extract, airflow rate, pH, and temperature significantly influenced lipid production in a preliminary study. The lipid production was scaled up to 5 L capacity airlift bioreactor and its optimization was done by response surface methodology. The dried yeast biomass obtained under optimized conditions from 5 L bioreactor was subjected to a direct transesterification process. Biomass: methanol ratio, catalyst concentration, and time were the variables used to attain higher FAME yield in the transesterification optimization process.ResultsUnder optimized conditions, the highest lipid yield of 2.68 g L–1 was obtained with 15.33 g L–1 of starch content, 0.5 g L–1 of yeast extract, and 5.992 L min–1 of airflow rate in a bioreactor. The optimized direct transesterification process yielded a higher FAME yield of 86.56% at 1:20 biomass: methanol ratio, 0.4 M catalyst concentration, and a time of 6.85 h.ConclusionsThus, this optimized process rendered the microbial lipids derived from C. tropicalis ASY2 as potentially alternative oil substitutes for sustainable biodiesel production to meet the rising energy demands.

Use of dry yeast biomass as a new approach for detoxification of hemicellulosic hydrolysates aiming to xylitol production

The presence of toxic compounds in hemicellulosic hydrolysates is a bottleneck for biotechnological processes, such as xylitol production. In our work, a new approach was proposed for hemicellulosic hydrolysates detoxification by using the residual dry yeast biomass (DYB) from xylitol production bioprocess. Candida tropicalis biomass was recovered from fermentation process of a medium based on sugarcane bagasse and straw hemicellulosic hydrolysate (SBSH). The effects of influent variables on detoxification performance were investigated, and the removal of phenolic compounds, acetic acid, furfural and 5-hydroxymethylfurfural reached up to, respectively, 27.0 %, 26.7 %, 27.5 %, and 25.8 %. By using the SBSH detoxified at conditions of highest phenolics removal, fermentations (initial xylose concentration of 52 g L−1) were performed for xylitol production, resulting in a yield of 0.79 gg-1 and 86 % of conversion efficiency. Thus, the use of residual DYB is a potential alternative for detoxification of hemicellulosic hydrolysates, since recycling the biomass could reduce the expenditures with adsorbents.

Optimization of baker`s yeast production on grape juice using response surface methodology

There is an increasing interest in improving biological processes, including fermentation processes, improving fermentation conditions is difficult, as it requires the use of an appropriate improvement method that allows operating the biological fermenter under optimal conditions in order to obtain the largest possible amount of the final product. The aim of this work was to succeed in examples of fermentation conditions to produce the largest possible quantity of dry yeast biomass Saccharomyces cerevisiae using grape juice as the sole carbon source. The optimum values of five factors that have an effect on the production of dry biomass from baker`s yeast were determined. The design of the experiments was carried out using the central composite experimental design (CCD) and the number of experiments according to the design was (54) experiments, the response surface methodology method was used to determine the best possible amount of production of yeast, and has reached (41.44 g/L) after 12 hours of fermentation, under the following optimal conditions (temperature (30.11??), pH (4.75), sugar concentration (158.36 g/L), the ratio of carbon to nitrogen (an essential nutrient for yeast growth ) is (11.9), initial concentration of yeasts (2.5 g/L), the amount of urea was 6.65 g/L and the amount of ammonium sulfate used was 6.65 g/L, so that the concentration of added urea and ammonium sulfate was (50-50)% and the required C/N ratio was achieved, and the used agitation speed was equal to 200 r.p.m during the fermentation process. The fermenter power of the obtained yeast was 470 ml. Three kinematic models (Monod, Verhulst, and Tessier) were also selected for the purpose of studying the kinetic performance of Saccharomyces cerevisiae yeast. Monod and Tessier`s models did not give satisfactory results, while the best results were according to the Verhulst model. Also, the Leudeking Piret model has also been successfully used to predict substrate consumption during fermentation time.

Semi-continuous pilot-scale microbial oil production with Metschnikowia pulcherrima on starch hydrolysate

BackgroundHeterotrophic microbial oils are potentially a more sustainable alternative to vegetable or fossil oils for food and fuel applications. However, as almost all work in the area is conducted on the laboratory scale, such studies carry limited industrial relevance and do not give a clear indication of what is required to produce an actual industrial process. Metschnikowia pulcherrima is a non-pathogenic industrially promising oleaginous yeast which exhibits numerous advantages for cost-effective lipid production, including a wide substrate uptake, antimicrobial activity and fermentation inhibitor tolerance. In this study, M. pulcherrima was fermented in stirred tank reactors of up to 350 L with 250-L working volume in both batch and semi-continuous operation to highlight the potential industrial relevance. Due to being food-grade, suitable for handling at scale and to demonstrate the oligosaccharide uptake capacity of M. pulcherrima, enzyme-hydrolysed starch in the form of glucose syrup was selected as fermentation feedstock.ResultsIn batch fermentations on the 2-L scale, a lipid concentration of 14.6 g L−1 and productivity of 0.11 g L−1 h−1 were achieved, which was confirmed at 50 L (15.8 g L−1; 0.10 g L−1 h−1). The maximum lipid production rate was 0.33 g L−1 h−1 (daily average), but the substrate uptake rate decreased with oligosaccharide chain length. To produce 1 kg of dry yeast biomass containing up to 43% (w/w) lipids, 5.2 kg of the glucose syrup was required, with a lipid yield of up to 0.21 g g−1 consumed saccharides. In semi-continuous operation, for the first time, an oleaginous yeast was cultured for over 2 months with a relatively stable lipid production rate (around 0.08 g L−1 h−1) and fatty acid profile (degree of fatty acid saturation around 27.6% w/w), and without contamination. On the 250-L scale, comparable results were observed, culminating in the generation of nearly 10 kg lipids with a lipid productivity of 0.10 g L−1 h−1.ConclusionsThe results establish the importance of M. pulcherrima for industrial biotechnology and its suitability to commercially produce a food-grade oil. Further improvements in the productivity are required to make M. pulcherrima lipid production industrial reality, particularly when longer-chain saccharides are involved.

Rhodosporidium sp. GROWTH IN MOLASSES MEDIUM AND EXTRACTION OF ITS ASTAXANTHIN BY USING HCl

Astaxanthin is classified as a xanthophyll-carotenoid, which is red-orange colour and powerful antioxidant activity. In this study, astaxanthin was collected from Rhodosporidum sp. by pilot culture (10 liters). Molasses medium was investigated with urea ((NH4)2CO), magnesium sulfate heptahydrate (MgSO4.7H2O) and potassium dihydrogen phosphate (KH2PO4) at different concentrations. Astaxanthin was extracted by using chlorhydric acid (HCl) method.The highest dried yeast biomass was 8.3682 g/l culture supernatant and astaxathin was 1.932 g/l culture supernatant by molasses medium containing 20 g/l sugar, 0.5 g/l ((NH4)2CO, 3 g/l MgSO4.7H2O and 10 % (v/v) inoculum. HCl extraction method was mixed 10 mg biomass: 1 ml HCl 0.6 N and incubated at 70 oC, 150 minutes.

RESISTANCE OF RHODOTORULA RUBRA g2/1 TO HEAVY METALS AND THEIR ADSORPTION

The aim was to study the level of resistance of the strain Rhodotorula rubra g2/1 to the heavy metals Cu, Zn, Pb, Cd and adsorption of them by the yeast cells. Red yeast strain Rhodotorulla rubra g2/1 was isolated by seeding on nutrient medium Saburo from the coastal waters of the Zmiiniy Island. The estimation of the influence of ions of heavy metals on physiology of yeast growth was conducted on Reader medium with addition of various concentrations of heavy metals Cu, Zn, Pb, Cd. The content of the metals in the investigated samples was determined with the atomic absorption spectrophotometer “Saturn-2”. The minimal concentrations of heavy metals inhibited the growth of yeast strain Rhodotorula rubra g2/1 were determined. They are 750 mg/l for copper, 500 mg/l for zinc, 120 mg/l for lead, 10 mg/l for cadmium. Thus, the studied yeast strain is the most resistant to copper and the most sensitive to cadmium. During incubation of the yeast in solutions containing heavy metals for 2 hours they remove 85.6% of copper, 18.6% of lead, 7.8% of cadmium, 7.7% of zinc. One gram of dry yeast biomass accumulates 90.0 mg of copper, 38.9 mg of cadmium, 12.9 mg of zinc and 26.2 mg of lead. Thus, the conducted investigations have shown that the yeast strain Rhodotorula rubra g2/1 simultaneously possesses high levels of resistance to copper and the ability to absorb this metal.

Growth performance, feed utilisation and fatty acid deposition in Atlantic salmon, Salmo salar L., fed graded levels of high-lipid/high-EPA Yarrowia lipolytica biomass

Salmon aquaculture is currently reliant on fish oil as the major source of the very long chain (VLc) n−3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). This report details the first study of an alternative source of EPA from the yeast Yarrowia lipolytica in feed for fish. Atlantic salmon was fed three dietary levels, 10% (Y10), 20% (Y20) and 30% (Y30) of a heat killed dried yeast biomass containing 6% EPA and 20% oil by weight for 95days. The yeast biomass was replacing fish meal, rapeseed oil and wheat meal in the diets. The increase in fish weight from 180 to 400g on the diets containing yeast, was comparable to groups fed control diets with either rapeseed oil (RO) or a mix of rapeseed and fish oil. The apparent digestibility coefficient for energy, protein and lipids, including n−3 fatty acids, decreased with increased inclusion of yeast biomass. Feed conversion ratio was higher, and energy retention lower, in the Y30 group than in the others. Protein retention was the lowest in the Y30 and FO groups followed by Y20. Fillet fatty acid composition reflected the higher ratio of EPA to DHA in the feeds added yeast. However, lower whole body retention of EPA, and higher retention of DPA (docosapentaenoic acid) and DHA, compared to average fatty acid retention, suggest that there had been some conversion of the EPA provided by the yeast into DPA (docosapentaenoic acid) and DHA in fish.

On-line carbon balance of yeast fermentations using miniaturized optical sensors

Monitoring of microbiological processes using optical sensors and spectrometers has gained in importance over the past few years due to its advantage in enabling non-invasive on-line analysis. Near-infrared (NIR) and mid-infrared (MIR) spectrometer set-ups in combination with multivariate calibrations have already been successfully employed for the simultaneous determination of different metabolites in microbiological processes. Photometric sensors, in addition to their low price compared to spectrometer set-ups, have the advantage of being compact and are easy to calibrate and operate. In this work, the detection of ethanol and CO(2) in the exhaust gas during aerobic yeast fermentation was performed by two photometric gas analyzers, and dry yeast biomass was monitored using a fiber optic backscatter set-up. The optical sensors could be easily fitted to the bioreactor and exhibited high robustness during measuring. The ethanol content of the fermentation broth was monitored on-line by measuring the ethanol concentration in the fermentation exhaust and applying a conversion factor. The vapor/liquid equilibrium and the associated conversion factor strongly depend on the process parameter temperature but not on aeration and stirring rate. Dry yeast biomass was determined in-line by a backscattering signal applying a linear calibration. An on-line balance with a recovery rate of 95-97% for carbon was achieved with the use of three optical sensors (two infrared gas analyzers and one fiber optic backscatter set-up).

Biomass Production by Antarctic Yeast Strains: An investigation on the Lipid Composition

ABSTRACTPsychrophilic yeast strains Rhodotorula glutinis AL107, Sporobolomyces roseus AL108, Cryptococcus albidus AL55, Cryptococcus laurentii AL56 and Cryptococcus laurentii AL58 isolated from soil sample taken from the region of the Bulgarien base on Livingston Island, Antarctica, were studied. The biomass production was followed after cultivation of the yeasts in a medium with pH 5.3 at 15°C for 120 h. The biomass concentration by psychrophilic yeast strains was: R. glutinis AL107-6.05 g/l, S. roseus AL108-5.78 g/l, Cr. albidus AL55, Cr. laurentii AL56 and Cr. laurentii AL58-6.52 g/l, 6.84 g/l and 6.24 g/l, respectively.The extracted and separated lipids from the samples were supplied to analysis and the compositions of fatty acids, phospholipids, sterols as well as tocopherols were determined. Unsaturated fatty acids, mainly oleic (58.6–63.5%) and of saturated palmitic (18.2–24.5%), predominated in triacylglycerols. Sterols (0.1–0.3%) were valued in the dry yeast biomass. The content of phospholipids, mainly phosphatidylcholine, phosphatidylinositole and phosphatidylethanolamine was found to be in the range of 0.2–1.6%. The quantity of tocopherols was 0–26.3 mg/kg. All of tocopherol classes were established.

(−)Geosmin sorption by enological yeasts in model wine and FTIR spectroscopy characterization of the sorbent

For the first time, we report that enological yeasts or yeast cell walls can sorb (−)geosmin, an undesirable molecule that causes critical organoleptic defects in wine at low concentrations (around 50 ng l −1). The wine is described as “earthy” or “mouldy”. The influence of various post-harvesting processes on yeast (−)geosmin sorption capacity was studied. The dried yeast biomass obtained by the different processes was analysed by FTIR spectroscopy in ATR mode: structural differences were detected between the samples depending on the strain and the treatment used. Surface proteins and mainly phospholipids from the plasma membrane appeared to induce significantly different signals which may explain the different sorption capacities. The possible involvement of phospholipids in (−)geosmin sorption by yeasts highlights the complexity of this phenomenon. The post-harvesting processes were: spray-drying, mechanical cell disruption, autolysis and two methods of rehydration of dried yeast samples. The results show that, using the optimal combination of processes, the initial (−)geosmin concentration in model wine can be decreased by more than 50%.

Biosorption of copper(II) ions from aqua solutions using dried yeast biomass

The ability of dried yeast Saccharomyces biomass to remove Cu(II) ions from aqueous solutions was investigated by using of batch techniques. The influence of different parameters on copper uptake by dried yeast, such as initial Cu(II) concentration, initial pH of solution and temperature, was studied. The Freundlich, Langmuir, Redlich–Peterson and Sips isotherms were applied to the obtained experimental data. According to Langmuir isotherm the maximum adsorption capacity of investigated non-living biomass was found to be 2.59 mg/g. The thermodynamic parameters (e.g. free energy and enthalpy) were calculated and discussed. The adsorption of Cu(II) onto the dried cells of Saccharomyces cerevisiae is an endothermic process and become more favorable with the increasing of temperature in pH range from 3 to 4. Optimization studies by means of response surface methodology were carried out, which resulted in improvement of the efficiency of sorption removal by using of biomass. The removal efficiency of real wastewater originating from electroplating industry which contains Sn(II) ions was determined and compared with synthetic wastewater obtained in laboratory.

Use of the industrial yeastCandida utilis for cadmium sorption

The sorption ability of Candida utilis biomass for cadmium ions with accumulating competence of dried cells and cells in alginate was compared. After an optimization of process conditions (pH 5.5, biomass concentration 1 g/L and c0 50 mg/L), the cadmium sorption capacity of dried yeast biomass was perceptibly higher than that of the other tested adsorbents. Considering the sorption of the dried yeast biomass equal to 100 %, the cells in alginate reached 86 % while native cells showed only 42 %.

Removal of copper ions from dilute solutions byStreptomyces noursei mycelium. Comparison with yeast biomass

Sorption properties of Streptomyces noursei mycelium for copper ions were compared with the accumulation competence of dried and native yeast (Candida utilis) biomass. The copper sorption capacity of S. noursei after optimization was found to be higher than that of the two other adsorbents (dried yeast biomass 82 %, native Candida cells 48 % of the sorption capacity of the S. noursei mycelium).

Effect of cultivation mode on a bioprocess for chromium yeast biomass enrichment.

Defined cultivation media for yeast growth which contained 278.8 mM of glucose and 0.1 mM of chromium(III) added as K2Cr(SO4)2· 12 H2O was used in batch and combined batch/fed-batch cultivation mode. In fed batch cultivation mode the rate of substrate addition remained constant during growth of yeast and corresponded to a growth rate of 0.25 h-1. In both cases the growth and yeast activity was followed by on line measurement of optical density, pH and pO2 at 30°C. At the end of the bioprocess the concentration of protein in yeast biomass was determined off line by the biuret reaction. Total and organically bound chromium was detected by ETA-AAS. Different cultivation modes affected the total cell protein concentration of yeast grown in media supplemented with chromium. In batch process the protein content represented 25.7% of dry yeast biomass, in contrast in the mixed bioprocess this value was 16.9% one the same period of time. The influence of cultivation mode on chromium uptake was seen in total chromium accumulation which reached 8.68 ± 0.16 μmol g-1 d.wt. in batch and 1.92 ± 0.04 μmol of chromium g-1 of dry yeast biomass in combined batch/fed-batch cultivation mode. The opposite was observed for organically bound chromium. The 60 % of total accumulated chromium was organically bound during yeast growth in combined batch/fed-batch mode. When yeast was grown in batch mode this value attained 13.5 %. Results suggested that a combined batch/fed-batch mode of cultivation was more effective over a batch system in chromium biotransformation to organically bound chromium, regardless of the lower protein ratio determined in the yeast biomass.