As a response to the increasing demand for ethanol as a renewable energy source, the design of a bioreactor to facilitate efficient glucose fermentation by Saccharomyces cerevisiae is very essential. Although a number of mathem atical models that gave some parameters used for bioreactor design can be found in the literature, only a few models were designated for fermentation using immobilized S. cerevisiae. This study aimed to develop an unstructured fermentation kinetics model based on the mass transfer phenomena and the Monod equation to describe the rate of glucose consumption, glucose concentration on the bead surface, yeast cell growth, and ethanol concentration. Four ordinary differential equations obtained from the model development were solved simultaneously using fourth order Runge-Kutta with the help of MATLAB software. The accuracy of the model was verified with the experimental data collected from the relevant literature with the average error (%) of the variation of loading yeast mass, pH, and temperature were 5.12–10.08, 3.63–7.95, and 5.35–11.87, respectively. Seven adjustable kinetic parameters were also successfully obtained for a quantitative description of bioethanol production from fermentation of glucose employing S. cerevisiae immobilized on sodium alginate beads. The simulation results proved that the proposed model can accurately predict the concentration of glucose and ethanol in the fermentation broth, concentration of glucose on the alginate beads surface, and yeast cell concentration. Hence, the model can be potentially applied for the design of a larger scale batch bioreactor for glucose fermentation using S. cerevisiae immobilized on sodium alginate beads for ethanol production.

One of the microalgae that can be potentially used to produce bioethanol is Chlorella vulgaris, as it is rich in carbohydrates. However, the carbohydrates in C. vulgaris cannot be converted directly into ethanol. This study aimed to investigate the chemical and enzymatic hydrolysis of C. vulgaris, which is subsequently followed by fermentation. The catalysts used in the chemical hydrolysis were hydrochloric acid, sodium hydroxide, and potassium hydroxide, while the enzymes used were the mixture of alpha-amylase + glucoamylase, alpha-amylase + cellulase, and alpha-amylase + glucoamylase + cellulase. The hydrolysate obtained from chemical hydrolysis was fermented through Separate Hydrolysis Fermentation (SHF), while the one from enzymatic hydrolysis was fermented through Simultaneous Saccharification and Fermentation (SSF), in which both processes used S. cerevisiae. After undergoing five hours of enzymatic hydrolysis (using alpha-amylase + glucoamylase), the maximum glucose concentration obtained was 9.24 ± 0.240 g/L or yield of 81.39%. At the same time and conditions of the substrate on chemical hydrolysis, glucose concentration was obtained up to 9.23 + 0.218 g/L with a yield of 73.39% using 1 M hydrochloric acid. These results indicate that chemical hydrolysis is less effective compared to enzymatic hydrolysis. Furthermore, after 48 hours of fermentation, the ethanol produced from SHF and SSF fermentation methods were 4.42 and 4.67 g/L, respectively, implying that producing bioethanol using the SSF is more effective than the SHF method.

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.

Bioethanol is alternative renewable energy typically obtained from glucose through a fermentation process using Saccharomyces cerevisiae. In the bioethanol fermentation process using yeast, there are several inhibiting factors, such as a high concentration of substrate, ethanol as the product, and nutrients. The present study aimed to investigate the effect of fermentation time (12- 72 hours), immobilized carrier size (sizes of 0.5 cm3 , 1 cm3 , and 1.5 cm3 ), and medium pH (3.0, 4.0, and 5.0) on the ethanol fermentation process using immobilized yeast in jackfruit (Artocarpus heterophyllus) seeds and subsequently to compare its performance with a free cell system. The highest ethanol concentration (89.15 g/L) with a yield of 96.92% was obtained by immobilizing yeast in jackfruit seed at a fermentation time of 72 hours, carrier size of 0.5 cm3 , and medium pH of 5.0. When compared to the free cell system fermentation under identical operating conditions, immobilized yeast in jackfruit seed obtained 1.41 times higher ethanol concentration. Jackfruit seed also led to a higher ethanol concentration compared to other S. cerevisiae carriers. Altogether, our findings imply that jackfruit seed has great potential as a carrier of S. cerevisiae in the process of fermenting glucose into ethanol

The need for food in the world is currently increasing, one of high consumption is rice. Analog rice is one of the products for rice substitute consumption to meet staple food with better nutritional value. In this research, the production of analog rice was made from fermented sorghum using Rhizopus oligosporus which has been studied previously with the addition of soybean flour fortification. Raw materials of sorghum grain were fermented using Rhizopus oligosporus to reduce tannin levels of sorghum and the addition of fortified soybean flour aims to increase the nutrition of analog rice. Analog rice production is carried out using the extrusion method with fermented sorghum flour with fortified soybean flour in a ratio of 0 to 50%. Nutritional value of analog rice (carbohydrates, protein, fat, fiber, minerals, and water), morphology, water adsorption index (WAI), water solubility index (WSI), hydrophilicity, and consumer acceptance were characterized. The best nutritional of analog rice produced was obtained from the combination of 50% sorghum (red or white sorghum) and 50% soybean flour, which contained carbohydrates, protein, fat, and fiber of 58.29%, 17.07%, 14.47%, and 7.43% respectively. The increasing portion fortified of soybean flour was reduced the WAI and increased the density of the analog rice structure. These characteristics are friendly to diabetic patients since they are rich in carbohydrates, protein, and fiber. On the other hand, this analog rice has the potential to be consumed as a main food ingredient to replace paddy rice and develop to staple food. Moreover, the insignificant effect of the WSI value and hydrophilicity of the analog rice were observed. However, adding soybean flour as a substitute for analog rice was less attractive to consumers than analog rice without substitutes.

Amorphophallus oncophyllus or commonly known as porang is a group of Aracea tubers. Porang has a high economic value and prebiotic source of oligosaccharides because it contains glucomannan. Porang flour contains about 67.5% glucomannan. Glucomannan is used as an emulsifier and stabilizer in the food, beverage and cosmetics products industry and as an ingredient for supplements and food additives because of its high fibres content. In this study, glucomannan purification can be optimized by using chemicals with modified maceration techniques with a stirring and washing machine using ethanol and glucomannan analysis using phenol sulphuric acid test in order to determine the decrease in sugar in porang flour. The purpose of this study was to determine the highest glucomannan content from several parameters such as the concentration of hydrochloric acid catalyst, stirring time, temperature, and the ratio of samples to solvents. The optimum conditions for the extraction process were at 0.7 M hydrochloric acid catalyst concentration, stirring time for 1 hour, temperature at 70°C and the ratio of samples to solvents was 1:5. Therefore, the optimum glucomannan content obtained from extraction using hydrochloric acid catalyst reached 95.85%.