Selection and the Growth Condition Optimization of Ethanol‐Producing Microbes Isolated from Ragi Tapai

Ethanol is a biofuel produced from renewable resources, which potentially plays an important role in solving future fuel problems. This study aimed to select the highest ethanol-producing isolate from candidates obtained from previously isolated candidates from ragi and cassava tapai. The selection process was conducted in 2 stages, namely: 1) Selection of the highest ethanol-producing isolate from seven isolate candidates using PYG media containing peptone, yeast extract, and glucose at 0.75%, 0.75%, and 15%, respectively and was followed by: 2) Optimization of the growth conditions of the highest ethanol-producing isolate, which was conducted at various temperatures of 27, 30, 33, 35, 37, and 40°C with the combination of various pH of 3.5, 4.5, 5.5, and 6.5. The experimental results showed that the R5I3 isolate was the highest ethanol-producing performance isolate, which yielded approximately 4.69±0.25% (v/v). Following the temperature and pH optimization of the fermentation processes, the optimum growth conditions were at 35°C and pH 5.5, where the ethanol produced was increased to 8.63 ± 0.04% (v/v). With these results, this new strain has the potential to be used in bioethanol production processes and other industrial applications

The Effect of Mixed Inoculum Addition Concentration and Fermentation Time on the Characteristics of Dry Cocoa Beans (Theobroma cacao L.)

The fermentation process has an important role in determining the quality of cocoa beans by forming taste, color, aroma, and appearance. The purpose of this study was to determine the effect of inoculum concentration and fermentation time on the characteristics of dry cocoa beans and determine the best conditions for both inoculum addition concentration and fermentation time to produce dry cocoa beans under Indonesian national standards. The research used completely randomized design with two factors; the first factor was the starter concentration consisting of controls (0%), 0.5%, 1%, 1.5%, and 2% (v/w). The second factor is the fermentation time, namely 1 day, 2 days, 3 days, 4 days, and 5 days. Treatment was repeated twice to get 50 units of the experiment. The results showed that the addition concentration of mixed inoculum (Saccharomyces cerevisiae and Lactobacillus plantarum) had a significant effect on changes in temperature and pH during fermentation, and it also had a significant effect on total unfermented beans. This study showed that time fermentation treatment had a very significant effect on all tests. The interaction of the two treatments had a significant effect on temperature changes during fermentation; it also significantly affected total unfermented beans. According to the Indonesian National Standard of cocoa beans, the best treatment, and the fastest fermentation time to produce the first quality standard (cut test) is a concentration of 1% mixed inoculum and fermentation in 3 days