Metabolism of cheese whey lactose by kluyveromyces fragilis for energy and growth under batch condition

The fermentation of lactose byKluyveromyces fragilis is an exothermic reaction in which heat is released, resulting in a rise in reactor temperature. A heat balance was performed on a 5-L batch reactor used for single cell protein (SCP) production to determine the portions of cheese whey lactose used for energy and growth. On the average, about 88% of lactose was used for growth, and 12% was used for energy. The lactose consumed during the lag and stationary phases was used mostly for cell endogenous growth and respiration, whereas that consumed during the exponential growth phase was used for cell multiplication and energy. The heat released varied from 6.5 to 8.9 kJ/g cell. Because of the proper design of the fermenter, the temperature of the medium did not rise above 33°C; thus, no cooling system was needed.     

Nutritional profile of food yeast kluyveromyces fragilis biomass grown on whey

Biomass of food yeast Kluyveromyces fragilis (MTCC 188) grown on deproteinized whey supplemented with 0.8% diammonium hydrogen phosphate and 10 ppm indole-3-acetic acid, had a crude protein content of 37%. The true protein content based on nitrogen fractionation procedure was 28.1%. Total nucleic acid content was 4.82%. This amount does not appear to be toxicologically offensive. Crude fiber, ash, and lipid content of K. fragilis dry cells were found to be 4.9%, 16%, and 7.8%, respectively. Essential fatty acids of both ω-3 and ω-6 series were found present in the fat of the yeast and represented 21.5% of the total fatty acids. All the essential amino acids were present in the proteins of K. fragilis; however, sulfur containing amino acids were found in lower amounts. Calculated protein scores indicate moderate biological value. Bvitamins in the biomass were present as expected, but folic acid and pyridoxine were present in high concentration.     

Effect of pH control on the growth and survival ofKluveromyces fragilis in cheese whey under aerobic condition

Many biological and chemical systems involve acid-base equilibria and thus depend critically on the pH of the solution. Small fluctuations of pH must be corrected by the addition of an acid or base to maintain the pH at the required optimum level during the fermentation process. The effect of pH control on the growth ofKluveromyces fragilis, used for the production of single-cell protein from cheese whey, was investigated. Maintaining the pH at 4.5 was found essential for the survival of the yeast. Without pH control, the pH of the medium continued to rise, resulting in the death and/or sporulation of the yeast cells. Diauxic growth was observed, caused by the growth of contaminant bacteria when the pH was not controlled.     

Continuous propagation ofKluyveromyces fragilis in cheese whey for pollution potential reduction

A 25-L working volume, upright cylindrical fermenter made of stainless steel was used to investigate cheese whey yeast fermentation for pollution potential reduction. The effluent total and soluble chemical oxygen demand, total and volatile solids, and total Kjeldahl and ammonium nitrogen concentrations were significantly affected by the hydraulic retention time, air flow rate, and mixing speed. The system removal efficiencies were 15.90-58.61%, 25.20-69.33%, 12.43-49.90%, 9.22-51.77%, 1.66-10.06%, and 54.82-72.22% for total chemical oxygen demand, soluble chemical oxygen demand, total solids, volatile solids, total Kjeldahl nitrogen, and ammonium nitrogen, respectively, depending on the hydraulic retention time, air flow rate, and mixing speed used.     

Bacterial production of PHA from lactose and cheese whey permeate

Due to the large availability of agro-industry wastes containing potentially exploitable substrates, such as whey from dairy industry, a study on the bacterial conversion of lactose and whey permeate to poly(β-hydroxyalkanoate) (PHA) was undertaken. A first approach was carried out on culture collection strains. Among a number of strains tested, Hydrogenophaga pseudoflava DSM 1034 and Sinorhizobium meliloti 41 were found to grow on lactose and produce PHA. These findings suggested to investigate among a wider range of microorganisms by directly isolating new strains from soil. A number of soil bacteria were first isolated on a minimal medium containing lactose as unique carbon source and PHA-accumulating traits were then investigated. Three isolates, identified by 16S rDNA sequence analysis as Sinorhizobium sp., Bacillus megaterium and Bacillus sp., were selected for their efficient growth and PHA production using lactose as carbon source. The same strains were also tested for their ability to accumulate PHA by direct fermentation of whey and whey permeate. Our results suggest that production of the polymer from cheese whey or whey permeate may be possible, although further research is needed to determine whether these microorganisms have the potential for commercial production of such biodegradable polymers.     

A mathematical model of ethanol fermentation from cheese whey

The cybernetic approach to modeling of microbial kinetics in a mixedsubstrate environment has been used in this work for the fermentative production of ethanol from cheese whey. In this system, the cells grow on multiple substrates and generate metabolic energy during product formation. This article deals with the development of a mathematical model in which the concept of cell maintenance was modified in light of the specific nature of product formation. Continuous culture data for anaerobic production of ethanol byKluyveromyces marxianus CBS 397 on glucose and lactose were used to estimate the kinetic parameters for subsequent use in predicting the behavior of microbial growth and product formation in new situations.     

Pollution potential reduction of cheese whey through yeast fermentation

Batch and continuous pilot-scale aerobic fermenters of 4.8 L operating volume were designed and constructed from plexiglass materials. The fermenters were used to study the kinetics of cheese whey fermentation using the yeast K. fragilis for pollution potential reduction and single cell protein production. Four retention times (6, 12, 18, and 24 h) were used in this study. The fermentation process was successful in reducing the total chemical oxygen demand (COD) by 42%, the soluble COD by 65%, the total solids by 53%, and the ammonium nitrogen by 90%. There were also gains in the suspended solids and the organic nitrogen of 60 and 17%, respectively. The reductions in the COD, total solids, and ammonium nitrogen, and the gains in the suspended solids and organic nitrogen were affected by the hydraulic retention time. More soluble material was converted to insoluble microbial cells at the 12-h hydraulic retention time, whereas greater pollution potential reduction was achieved at the 24-h hydraulic retention time for both batch and continuous operations.     

Amelioration of methane yield in cheese whey fermentation by controlling the pH of the methanogenic stage

A two-stage, no-mix anaerobic digester of 145 L capacity was used to investigate the effect of controlling the pH of the methanogenic stage on the biogas production and the pollution potential reduction of acid cheese whey. The digester was operated at a 15-d hydraulic retention time, and a temperature of 35°C. Controlling the pH of the methanogenic stage increased the biogas production rate and methane yield by 77.77 and 289.00%, respectively. Reductions of up to 32.19, 44.44, and 35.86% in the COD, solids and nitrogen were achieved.     

A novel fermentation process for calcium magnesium acetate (CMA) production from cheese whey

Applied Biochemistry and Biotechnology - A novel, anaerobic fermentation process is developed to produce calcium magnesium acetate (CMA) from cheese whey. CMA can be used as a noncorrosive road...     

Lactic acid recovery from cheese whey fermentation broth using combined ultrafiltration and nanofiltration membranes

The separation of lactic acid from lactose in the ultrafiltration permeate of cheese whey broth was studied using a cross-flow nanofiltration membrane unit. Experiments to test lactic acid recovery were conducted at three levels of pressure (1.4, 2.1, and 2.8 MPa), two levels of initial lactic acid concentration (18.6 and 27 g/L), and two types of nanofiltration membranes (DS-5DK and DS-5HL). Higher pressure caused significantly higher permeate flux and higher lactose and lactic acid retention (p<0.0001). Higher initial lactic acid concentrations also caused significantly higher permeate flux, but significantly lower lactose and lactic acid retention (p<0.0001). The two tested membranes demonstrated significant differences on the permeate flux and lactose and lactic acid retention. Membrane DS-5DK was found to retain 100% of lactose at an initial lactic acid concentration of 18.6 g/L for all the tested pressures, and had a retention level of 99.5% of lactose at initial lactic acid concentration of 27 g/L when the pressure reached 2.8 MPa. For all the test when lactose retention reached 99–100%, as much as 64% of the lactic acid could be recovered in the permeate.     

Anaerobic upflow fixed-film bioreactor for biomethanation of salty cheese whey

In order to develop a suitable reactor for the biomethanation of high-strength salty cheese whey, the performance of anaerobic upflow fixed-film reactors packed with different support materials, such as charcoal, gravel, brick pieces, pumicestones, and PVC pieces, has been studied. The charcoal-bedded reactor gave the best performance, with the maximum gas production (3.3 L/L digester/d) and an enriched methane content (69% CH₄). Temperature and hydraulic retention time were optimized, with the ultimate aim of improving biomethanation. Maximum gas production (3.3 L/L digester/d) was achieved at a hydraulic retention time of 2 d at 40°C.     

Simultaneous production of nisin and lactic acid from cheese whey

A biorefinery process that utilizes cheese whey as substrate to simultaneously produce nisin, a natural food preservative, and lactic acid, a raw material for biopolymer production, was studied. The conditions for nisin biosynthesis and lactic acid coproduction by Lactococcus lactis subsp. lactis (ATCC 11454) in a whey-based medium were optimized using statistically based experimental designs. A Plackett-Burman design was applied to screen seven parameters for significant factors for the production of nisin and lactic acid. Nutrient supplements, including yeast extract, MgSO₄, and KH₂PO₄, were found to be the significant factors affecting nisin and lactic acid formation. As a follow-up, a central-composite design was applied to optimize these factors. Second-order polynomial models were developed to quantify the relationship between nisin and lactic acid production and the variables. The optimal values of these variables were also determined. Finally, a verification experiment was performed to confirm the optimal values that were predicted by the models. The experimented results agreed well with the model prediction, giving a similar production of 19.3 g/L of lactic acid and 92.9 mg/L of nisin.     

Effect of nutrient supplements addition on ethanol production from cheese whey usingCandida pseudotropicalis under batch condition

Candida pseudotropicalis ATCC 8619 was selected among nine strains of lactose fermenting yeast for the production of ethanol from cheese whey. The effects of three nutrients (ammonium sulfate (NH₄)₂SO₄, dipotassium hydrogen phosphate K₂HPO₄, yeast extract, and a combination of them) on the ethanol yield from cheese whey were investigated. The results indicated that no addition of nutrient supplement is necessary to achieve complete lactose utilization during the cheese whey ethanol fermentation. However, addition of a small concentration (0.005% w/v) of these supplements reduced the lag period and the total fermentation time and increased the specific growth rate of the yeast. Higher concentrations (0.01 and 0.015% w/v) of ammonium sulfate and dipotassium hydrogen phosphate inhibited the cell growth and reduced lactose consumption. The highest ethanol (21.17 g/L) was achieved using yeast extract at a concentration of 0.01% w/v, given a conversion efficiency of 98.3%. No indication of alcohol inhibition was observed in this study.     

Microscopic approach for the identification of cationic membrane fouling during cheddar cheese whey electroacidification

This is the first time that fouling of cation-exchange membranes during cheddar cheese whey electroacidification with bipolar membranes is reported. A mineral fouling was observed only on the cationic membrane side in contact with the base. The deposit was identified as magnesium hydroxide and this fouling was more important on the cation-exchange membrane situated close to the cathode. Little deposit was formed after six electroacidification runs, but on long time, the buildup of fouling film would lead after many electroacidifications to an important decrease of the system efficiency. Since, fouling of permselective membranes represents one of the major issues in electrodialytic processes, this result will be the basis for the determination of cleaning conditions allowing the prevention of such a fouling.     

Importance of growth form on production of hybrid antibiotic byStreptomyces lividans TK21 by fed-batch and continuous fermentation

A fermentation strategy, based on the controlled feeding of growthlimiting nutrients in order to maintain metabolic activity for extended periods, has been examined in the case of the production of a hybrid antibiotic by a transformed strain ofStreptomyces lividans TK21. The fed-batch operation did not improve the results obtained with batch operation. Continuous cultures on defined medium showed stable levels of biomass concentration, but antibiotic production ceased when continuous operation was started. The results obtained indicate the critical influence that morphology of the cell aggregates has on metabolic activity. The antibiotic is produced only in culture conditions providing growth in compact mycelial pellets.     

Determination of cows' milk in goats' milk and cheese by capillary electrophoresis of the whey protein fractions.

The use of capillary zone electrophoresis to determine the adulteration of cows' milk in goats' milk products is described. The detection and quantification of cows' milk was based on the presence of the specific whey proteins: the relative calibration curve is reported. The peaks of interest were well resolved by using sodium borate at pH 9.2 as background electrolyte in methyl-silanized capillaries. The minimum amount detectable of cows' milk was 2% in milk mixtures and 4% in cheeses. Restrictions due to genetic variability and possible heat treatments, on only one of the two types of milk employed, are taken into account. Qualitative analysis of goat-ewe-cow and goat-ewe samples are also reported.     

Biomethanation of a mixture of salty cheese whey and poultry waste or cattle dung

This paper describes the results of a study aimed at improving the efficiency of anaerobic digestion of salty cheese whey in combination with poultry waste or cattle dung. Best results were obtained when salty cheese whey was mixed with poultry waste in the ratio of 7:3, or cattle dung in the ratio of 1:1, both on dry weight basis giving maximum gas production of 1.2 L/L of digester/d with enriched methane content of 64% and 1.3 L/L of digester/d having methane content of 63% respectively. Various conditions such as temperature and retention time have been optimized for maximum process performance.     

Effect of the variation of the level of lactose conversion in an immobilized lactase reactor upon operating costs for the production of baker’s yeast from hydrolyzed cottage cheese whey permeate

Operating costs for the production of Baker’s yeast from hydrolyzed permeate from the ultrafiltration of cottage cheese whey were calculated as a function of the level of lactose conversion in the immobilized lactase reactor. These costs were calculated for the case of 90% conversion of lactose in the reactor and compared to those that result when running the reactor at lower conversions with recycle of unreacted lactose. Total operating costs were estimated by combining individual operating costs for the immobilized enzyme reactor, costs associated with processing a lactose recycle stream, and energy costs associated with cooling the reactor feed stream and sterilizing the hydrolysate stream. It was determined that operating costs are minimized at about 9.9 ￠/lb. of lactose when the reactor is run at approx. 72% conversion. This represents a savings of 2.4 ￠/lb. of lactose over the case of a once-through 90% conversion of lactose in the reactor.     

Production of lactic acid from cheese whey by batch and repeated batch cultures of Lactobacillus sp. RKY2

The fermentative production of lactic acid from cheese whey and corn steep liquor (CSL) as cheap raw materials was investigated by using Lactobacillus sp. RKY2 in order to develop a cost-effective fermentation medium. Lactic acid yields based on consumed lactose were obtained at more than 0.98 g/g from the medium containing whey lactose. Lactic acid productivities and yields obtained from whey lactose medium were slightly higher than those obtained from pure lactose medium. The lactic acid productivity gradually decreased with increase in substrate concentration owing to substrate and product inhibitions. The fermentation efficiencies were improved by the addition of more CSL to the medium. Moreover, through the cell-recycle repeated batch fermentation, lactic acid productivity was maximized to 6.34 g/L/h, which was 6.2 times higher than that of the batch fermentation.     

On-line monitoring during fermentation of whey based on ultrafiltration and liquid chromatography

A high-performance liquid chromatographic (HPLC) system, controlled by means of a programmer, is described for monitoring the conversion of sugars and the formation of acids during fermentation processes. An on-line automatic sampling system was developed in order to achieve systematic sampling of the fermentation broth. The fermentor is connected to the HPLC system through a tangential ultrafiltration unit. This system is integrated into an automatic HPLC line for routine analysis.