The Bioethanol Production from Oil Palm Empty Fruit Bunches Using Saccharomyces cerevisiae Immobilized on Sodium Alginate Beads

Bioethanol is an environmentally benign renewable energy commonly obtained from glucose fermentation using Saccharomyces cerevisiae. The purposes of this study are to investigate the effects of time, temperature, pH, immobilized yeast cell loading, beads reuse during ethanol production through batch fermentation of glucose derived from oil palm empty fruit bunches by S. cerevisiae immobilized on Na-alginate beads and to compare the performance of fermentation using immobilized yeast cells and that of using a free cell system. The results revealed that time, temperature, pH, yeast mass and beads reuse significantly affected the ethanol and final glucose concentrations. As expected, a maximum ethanol concentration was obtained from fermentation using immobilized yeast cells at 30 °C, pH 5, and immobilized yeast cell loading of 0.75 g for 48 hours. However, fermentation with a free cell system at the same conditions resulted in lower ethanol yield. The highest ethanol concentration of 88.125 g/L with a productivity of 1.84 g/L·h was achieved from the second cycle fermentation using of immobilized cells beads. The results suggest that an immobilized cell system exhibits great potential applications for improved ethanol production due to its ability to sustain the stability of cell activity, reduce contamination tendency, and protect yeast cells from any possible inhibitions.

Kinetic modeling of ethanol production by batch fermentation of sugarcane juice using immobilized yeast

Ethanol production via the batch fermentation of sugarcane juice using immobilized yeast has been studied. The influence of glucose concentration, ethanol concentration, and cell concentration (biomass) on the process rate throughout the period of fermentation has been investigated. Initial cell concentration was found to be 4.60 g/L saccharomyces cerevisiae. Biomass, ethanol and glucose concentrations were measured at different time interval during fermentation. The experimental data obtained were fitted using a variety of models for yeast growth. The logistic model gave the best fitting and was the basis for the development of the overall kinetic model. For ethanol formation, different model based on the logistic model for yeast growth were used to fit the experimental data and the leudeking – piret model was adopted because of its good fit. The leudeking – piret model was also adopted for substrate consumption. The estimated values of the kinetic parameters in the developed model were μm=0.04216hr-1, Xm = 6.2652g/L, α = 24.87149g/g.hr, Yx/s = 0.18292g/g and m = 0.008171g/g.hr. Therefore, a model based on the logistic equation of yeast growth, growth associated production of ethanol, and consumption of glucose for biomass and maintenance was found to accurately fit the production of ethanol from sugarcane.

A Novel Immobilization Method of Saccharomyces cerevisiae on Fermentation of Nipa Palm Sap for Fuel Grade Bioethanol Production

Nipa palm (Nypa fruticans) spreads abundantly in the mangrove forests of eastern coast of Sumatera Island, Indonesia. Nipa palm sap can be used as a very high-gravity (VHG) substrate for fermentation. In this research, batch fermentation of nipa sap with initial sugar content of 262.713 mg/ml using immobilized Saccharomyces cerevisiae yeast cells was studied. Immobilization of the yeasts in Na-alginate by droplet method and addition of 0.2% v/v Tween 80 and 0.5g/l ergosterol to the immobilized cells were first carried out. Then, the effect of cells weight percentage (5, 10, 15, and 20% w/v) and fermentation time (24, 36, 48, 60, 72, 84, and 96 hrs) on the bioethanol production were investigated. After, the analysis of bioethanol concentration was investigated using Gas Chromatography. The bioethanol production increased with the fermentation time until reaching a maximum value at all cell weights. Except with the 20% w/v, this peak was followed by a decrease in the bioethanol production at cell weights of 5, 10, and 15% w/v. This phenomenon may be explained by degradation of bioethanol into acetic acid resulting in the decreased concentration at the end of fermentation. The formation of acetic acid was characterized by decreases in the pH values of the fermentation medium. On the contrary, the bioethanol level tended to increase until the end of fermentation with the immobilized yeast cells of 20% w/v. High number of available immobilized yeast cells at the end of fermentation, accumulation of bioethanol produced at earlier times, and no further conversion of bioethanol to acetic acid could be the reasons for this increase. The optimum conditions for bioethanol production were 20% w/v cell weight and 96 hr fermentation time, at bioethanol concentration of 17.57% v/v.

Development of a paper-immobilized yeast biosensor for the detection of physiological concentrations of doxycycline in technology-limited settings

To combat pharmaceutical counterfeiting in low- and middle-income countries (LMIC), there is a need for improved low-cost, portable methods that monitor pharmaceutical concentrations relevant to dosage forms and physiological fluids.