Continuous ethanol production using immobilized yeast cells entrapped in loofa-reinforced alginate carriers

Abstract

A culture of Saccharomyces cerevisiae M30 entrapped in loofa-reinforced alginate was used for continuous ethanol fermentation in a packed-bed reactor with initial sugar concentrations of 200-248 g/L. Maximum ethanol productivity of 11.5 g/(L·h) was obtained at an ethanol concentration of 57.4 g/L, an initial sugar concentration of 220 g/L and a dilution rate (D) of 0.2 h-1. However, a maximum ethanol concentration of 82.1 g/L (productivity of 9.0 g/(L·h)) was obtained at a D of 0.11 h-1. Ethanol productivity in the continuous culture was 6-8-fold higher than that in the batch culture. Due to the developed carrier's high biocompatibility, high porosity, and good mechanical strength, advantages such as cell regeneration, reusability, altered mechanical strength, and high capacity to trap active cells in the reactor were achieved in this study. The immobilized cell reactor was successfully operated for 30 days without any loss in ethanol productivity. The average conversion yield was 0.43-0.45 throughout the entire operation, with an immobilization yield of 47.5%. The final total cell concentration in the reactor was 37.3 g/L (17.7 g/L immobilized cells and 19.6 g/L suspended cells). The concentration of suspended cells in the effluent was 0.8 g/L

Glucose(xylose) isomerase production by Streptomyces sp. CH7 grown on agricultural residues

“…Currently, ethanol is the major form of biofuel, and numerous technologies have been employed to improve its production (1,19,26). Furthermore, fuel ethanol production from hemicellulosic hydrolysates by Saccharomyces cerevisiae is of great economic interest as an alternative to fossil fuel (18).…”

Production of sorbitol by repeated batch fermentation using immobilized of Lactobacillus plantarum Strain (BAA-793) via Solid State Fermentation

“…The beads were stored at 4°C for further experiments. To improve the immobilization results, the ratio of CaCl 2 (0.2%) and NaCl (0.85%) that were used in solution preparation was 1:1, v/v (Yan et al, 2001;Bangrak et al, 2011;El-Borai et al, 2013).…”

“…After the sterilizing process, the samples were cooled. Then, 10% of beads of immobilized cells were put into the samples (Yan et al, 2001;Hsieh and Yang, 2004;Bangrak et al, 2011;El-Borai et al, 2013). The samples were purged with nitrogen gas in order to remove oxygen gas to maintain the anaerobic condition and then they were incubated at 35 o C. All the experiments were carried out in 3 sets to get their average values.…”

Microencapsulation of Baker’s Yeast in Gellan Gum Beads Used in Repeated Cycles of Glucose Fermentation

“…Nevertheless, recent studies [2][3][4] have pointed out the interest of attaching yeast to polymeric matrices. The following practical advantages of using immobilized yeast cells are important for industrial scale-up: (a) increasing productivity of the fermenter which will permit the use of important flow rates in a continuous operating mode, avoiding the yeast cells destruction and obtaining of high yields in the fermentation processes [5][6][7]; (b) improving the process control, which is done by the continuous operation, product separation, and removal of the metabolic inhibitors, as well as by the improving product recovery (continuous extraction); (c) permitting recycling of the biological catalyst; 2 International Journal of Polymer Science (d) maintaining the biocatalyst in a stable and active state (the extension of the stationary phase); (e) protecting sensitive cells against destruction (e.g., shear forces); and (f) reducing the risk of microbial contamination.…”