Continuous Ethanol Production from Cheese Whey Fermentation byCandida Pseudotropicalis

Abstract

Three pilot-scale continuous mix reactors of 5-L volume each were used to study the effects of retention time (18-42 hours) and initial substrate concentration (50-150 g / L ) on the cell yield, lactose consumption, and maximum ethanol concentration during continuous fermentation of cheese whey using the yeast Candida psuedotropicalis. A microaeration rate of 480 mL/min and a nutrient supplement (yeast extract) concentration of 0.1% uol/uol were used. The results indicated that the dissolued oxygen concentration, temperafure, cell concentration, lactose utilization rate, and ethanol concentration were affected by hydraulic retention time and initial substrate concentration. The highest cell concentration of 5.46 g / L and the highest ethanol concentration of 57.96 g / L (with a maximum ethanol yield of 99.6% from the theoretical yield) were achieued at the 42-hour hydraulic retention time and the I50 g / L initial substrate concentration, whereas the highest ceN yield was obserued at the 50 g / L initial substrate concenfration and the 36-hour hydraulic retention time. Lactose utilizations of 98, 91, and 83% were obtained with 50, 100, and 150 g / L initial substrate concentrations at the 42-hour hydraulic retention time. A pH control system was found unnecessary.

Comparison of ethanol production from cheese whey permeate by two yeast strains

“…kefyr in normal and concentrated WPS was almost the same, both the yeasts produced substantially more ethanol in concentrated WPS than in normal one (Tables 2 and 3). This result is in agreement with other workers (Ghaly andEl-Taweel 1997, Zafar andOwais 2006). However, Klu.…”

“…In this experiment, unconcentrated and concentrated cheese whey was used because direct fermentation of cheese whey with low lactose content (3-5% w/v) led to low ethanol concentrations (2-3% v/v) at the end of fermentation. These two yeasts have been studied individually (Zafar andOwais 2006, Ghaly andEl-Taweel 1997), but in none of the literature studies their fermenting ability has been compared. Thus, the present study was undertaken to investigate which out of Klu.…”

“…In order to determine the effects of pH and temperature on ethanol production, both the yeasts were exposed to varying pH (4.1-5.8) and temperature (25-37ºc) in unconcentrated and concentrated whey permeate supernatant. The pH of UF permeate supernatant was adjusted to 4.5±0.1 using concentrated citric acid (Merck, Germany) since growth substances as basic salts did not make any difference in pH adjustment (Ghaly andEl-Taweel 1997, Fox 1982). The fermented broth was transferred to the vessel up to 3/4 of its capacity for distillation.…”

Fermentation of deproteinized cheese whey powder solutions to ethanol by engineered Saccharomyces cerevisiae: effect of supplementation with corn steep liquor and repeated-batch operation with biomass recycling by flocculation

“…Second, the yeast viability and the plasmid stability remained high throughout the process ( Table 2), demonstrating that the strain is genetically stable and robust for industrial utilization. Finally, due to the substantial buffering capacity of the whey solutions, a pH control system was unnecessary, which simplifies industrial operation [4,10]. The deproteinized CWPS were acidified to minimize bacterial contamination and the pH kept at 4.2 ± 0.2 during fermentations.…”

Potential Environmental and Health Impacts of High Land Application of Cheese Whey

“…Several value added products have been produced from cheese whey using various fermentation techniques. These included: single cell protein [5][6][7][8] , ethanol [9] , organic acids [10] , biopolymers [11] , anti-icers [12,13] and biodegradable plastics [14] . Although, these processes have been proven to be technically feasible, they are still far from being economical.…”