Effect of some physico-chemical treatments on the kinetics of autolysed-yeast extract production from whey (original) (raw)
Related papers
2000
The effects of chemical, biochemical and physical treatments on lysis of baker’s yeast cells were studied at pH 5.2 and temperature 54 °C. An unstructured kinetic model of first order was developed to understand the mechanism of yeast lysis. The autolysis rate constant (k), yield factor for protein ( β P ), total carbohydrate (β C ) and autolysate (α A ) were sensitive to disruption methods. Since there were endogenous enzymes in the yeast cells such as proteinases, glucanases and carboxypeptidases, these enzymes were responsible for synergistic of cell disruption and their activity profiles were affected by different treating methods. From the determined results of amino acids composition in yeast autolysate, there were differences in amino acid content. The biochemical treated sample using 0.1% papain gave the highest total amino acid content among all analysed samples.
Journal of Food Engineering 82 (2007) 618–625, 2007
A mathematical model for ethanol fermentation with yeast Saccharomyces cerevisiae and b-galactosidase on a whey medium was developed. Kinetic parameters of biomass growth were estimated using the least squares method on the basis of experimental data obtained in batch culture of suspended yeast cells growing on glucose and in batch fermentation with immobilized enzyme and yeast cells growing on lactose. Kinetic constants of separation of ethanol by pervaporation was estimated using experimental fluxes of permeate and separation coefficients of ethanol from broth. The degree of sugars utilization and the ethanol concentration in bioreactor as well as the time of ethanol separation needed to obtain the desired final concentration of recovered product can be predicted by using this model. The model can be also used for the investigation of influence of operating conditions on the fermentation yield and on the product concentration from broth. It can help as well in the optimization of process and in planning of experiments.
Submerged Yeast Fermentation of Cheese Whey for Protein Production and Nutritional Profile Analysis
2011
In this study, ten whey samples collected from dairy industries in Rasht (Iran). Five lactose fermentative yeasts strains (designated A1 to A5) were isolated. Beta-galactosidase activity in the yeast strains showed that strain of Kluyveromyces marxianus designated as A2 had highest enzyme activity (up to 9012 EU/mL) and the most SCP production from whey with the yield of 12.68 g/L. Ammonium sulfate as nitrogen source had an increasing effect on biomass yield up to 30%. Crude fiber, lipids, carbohydrates and ash content of isolate dry cells were found to be 4.9, 7.23, 33.19 and 14.05%, respectively. The true protein content based on nitrogen fractionation procedure was 29.25%. The yeast biomass recovering by ultrafiltration reduced the total COD to 96.26% of its initial value in the raw whey.
Effect of culture conditions of Kluyveromyces marxianus on its autolysis, and process optimization
Bioprocess Engineering, 1998
Cultivation of the lactose-metabolizing yeast Kluyveromyces marxianus var. marxianus (formerly K. fragilis) on supplemented whey permeate resulted in cellular yield little affected by culture conditions in the ranges pH 2.3±5 and T 30±40°C. When autolysis was induced only by energy source de®ciency and thermal shock, cellular material solubilization depended slightly on autolysis temperature in the range T 45±60°C. On the contrary, the process was under tight control of culture conditions; when autolysis was carried out at 50°C with an initial dry cellular concentration of 50 g l A1 , a clear optimum was observed for cells cultivated at pH 4.5 and T 35°C. So the critical step of the autolytic process consisted in biosynthesis of lytic enzymes (during cell growth) rather than enzymatic progress (during autolysis). These results were compatible with a model previously proposed for Saccharomyces cerevisiae [1]. List of symbols t time (h) T temperature (°C) x total biomass (dry cellular weight) concentration (g l A1) Y X/S biomass on lactose yield Subscripts i initial f ®nal S.E.M. Scanning Electronic Microscopy
Ethanol production from non-food substrate is strongly recommended to avoid competition with food production. Whey, which is rich in nutrients, is one of the non-food substrate for ethanol production by Kluyveromyces spp. The purpose of this study was to optimize ethanol from different crude (non-deproteinized, non-pH adjusted, and non-diluted) whey using K. marxianus ETP87 which was isolated from traditional yoghurt. The sterilized and non-sterilized whey were employed for K. marxianus ETP87 substrate to evaluate the yeast competition potential with lactic acid and other microflora in whey. The effect of pH and temperature on ethanol productivity from whey was also investigated. Peptone, yeast extract, ammonium sulfate ((NH 4) 2 SO 4), and urea were supplemented to whey in order to investigate the requirement of additional nutrient for ethanol optimization. The ethanol obtained from non-sterilized whey was slightly and statistically lower than sterilized whey. The whey storage at 4 °C didn't guarantee the constant lactose presence at longer preservation time. Significantly high amount of ethanol was attained from whey without pH adjustment (3.9) even if it was lower than pH controlled (5.0) whey. The thermophilic yeast, K. marxianus ETP87, yielded high ethanol between 30 and 35 °C, and the yeast was able to produce high ethanol until 45 °C, and significantly lower ethanol was recorded at 50 °C. The ammonium sulfate and peptone enhanced ethanol productivity, whereas yeast extract and urea depressed the yeast ethanol fermentation capability. The K. marxianus ETP87, the yeast isolated from traditional yoghurt, is capable of producing ethanol from non-sterilized and non-deproteinized substrates.
Journal of Food Engineering 91 (2009) 240–249, 2009
Mathematical models for semi-continuous ethanolic fermentation in a whey medium employing coimmobilized Saccharomyces cerevisiae strain and b-D-galactosidase and for pervaporative product recovery from the resultant broth were developed. Kinetic parameters of biomass growth were estimated using the nonlinear least squares method on the basis of experimental data obtained from culture of suspended yeast cells grown in a mixture of glucose and galactose and during semi-continuous fermentation in a bioreactor in a whey medium with co-immobilized enzyme and yeast cells. Experimentally determined fluxes of ethanol and water from broth were applied for the estimation of kinetic constants of ethanol separation by pervaporation. The degree of sugar utilization and ethanol productivity in bioreactor as well as the time of ethanol separation needed to obtain the desired amount of product can be predicted using this model. The influence of selected operating parameters on the fermentation effectiveness was simulated based on the developed model.
Cod Removal of Whey with Mixed Yeast Culture and Improvement of Biomass Yield
2013
The aim of the research is to improve the yield of the biomass and to remove the organic matters of the whey by using a mixed culture of (Saccharomyces cerevisiae+ Kluyveromyces lactis) yeast at rate 1/1. The optimal conditions of growth of the mixed culture of the (Saccharomyces cervisiae+ Kluyveromyces lactis) have been identified on a Rider medium and they have been as follows : pH : 5.5 , air flow : 0.5 liter air ⁄liter whey ⁄min, and temperature: 30 C° The aerobic biological treatment technique of the whey has been achieved by using the mixed culture of (Saccharomyces cervisiae+ Kluyveromyces lactis) yeast at rate 1% and at the optimal and specified conditions of growth , So that the value of the COD can be reduced from 65000 mg ⁄ L to 514 mg ⁄ L with COD removal efficiency of 99.21% , and the forming biomass 3.53% .
2015
Protein recovery under sonication treatment and autolysis, also protein hydrolysis progress during enzymatic hydrolysis (using trypsin and chymotrypsin) and autolysis (using endogenous enzymes) were investigated in Saccharomyces cerevisiae and Kluyveromyces marxianus. Crude protein content of dried yeast cells were 53.22% and 45.6% for S.cerevisiae and K.marxianus, respectively. After 96 hrs of autolysis in the presence of ethyl acetate, protein recovery reached 59.74% and 77.18% for S. cerevisiae and K. marxianus, respectively and it was 53.66% and 55.17% for sonication treatment. The yeast protein solution obtained by sonication was hydrolyzed by trypsin and chymotrypsin. Autolysis, produced hydrolysates with higher degree of hydrolysis (DH) values as compared to the enzymatic hydrolysis. After 96 hours autolysis, DH increased to 48.75% and 39.51% for S. cerevisiae and K. marxianus respectively. Chymotrypsin was significantly more effective on K. marxianus protein with the DH valu...
Egyptian Journal of Agricultural Sciences, 2009
Three local strains of Saccharomyces cerevisiae (Sc 1, Sc 2 and Sc 3) and one strain of Kluyveromyces marxianus were used as pure or mixed cultures in a commercial medium, in order to compare their kinetic parameters and fermentation patterns. It was found that S. cerevisiae Sc 3 had the highest maximum specific growth rates on glucose (0.32 h-1) and on ethanol (0.11h-1). The yields of biomasses on glucose and on ethanol were the most important. A low yield of ethanol on glucose 0.33 (g/g) was obtained. Kinetic studies of continuous production of biomass from a mixture of whey permeate and starch hydrolysates using mixed culture of Saccharomyces cerevisiae Sc 3 and Kluyveromyces marxianus were performed. In the course of continuous culture on mixed substrate of whey permeate and starch hydrolysates "A", Kluyveromyces marxianus overgrew Saccharomyces cerevisiae. Whereas in the course of continuous culture on mixed substrate of whey permeate and starch hydrolysates "B" there was a stabilization of the coculture (Saccharomyces cerevisiae Sc 3 and Kluyveromyces marxianus).