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Generally, the microorganism involved in soybean fermentation for the production of tempeh is Rhizopus oligosporus. However, Saccharomyces cerevisiae, a type of β-glucan-producing yeast, is known to be present and grow in the fermentation process. This study was aimed at investigating yeast and fungal growth dynamics, β-glucan formation, and antibacterial activity against Escherichia coli during the fermentation after adding S. cerevisiae as an inoculum. The Randomized Complete Block Design (RCBD) was applied with two treatments and three repetitions. Three types of starter culture were S. cerevisiae, R. oligosporus, and the combination of both. The second treatment was fermentation time at room temperature ( 30 ± 2 ° C ) for 0, 8, 16, 24, 32, and 40 hours. The dynamics were observed every eight hours. The obtained data were tested using Tukey’s Honestly Significant Difference (HSD) test. The results indicated that yeast grew during this process from a single S. cerevisiae culture and a mixture of R. oligosporus and S. cerevisiae, but not from R. oligosporus alone. The yeast grew during and until the end of fermentation and decreased after 32 hours in the mixed cultures. The β-glucan formed in tempeh with all types of inoculum, but the antimicrobial activity against E. coli increased with fermentation time and was significantly different between treatments. The highest β-glucan content and antibacterial activity of tempeh are from the mixed culture. In conclusion, the addition of S. cerevisiae and R. oligosporus in soybean fermentation produced tempeh with the highest β-glucan content and antibacterial activity against E. coli. The presence of β-glucans suggests higher health benefits of tempeh.

Ethanolysis of PKO has been done by the addition of ethoxide ion solution {ethanol 90% containing 1% (w/w PKO) of NaOH} to 100 g PKO at the ratio of 1.0; 1.2; or 1.4 (w/w), each with the addition of glycerol 10% (w/w PKO) at 55-60°C, stirred at 1000 rpm for 3, 6, 9, or 12 minutes. Careful observation is done on the yield and monoglyceride, diglycerides, and triglycerides distribution patterns in the PKO ethanolysis products. The average yield of all treatments resulted in a value of 44.91% (± 4.47%; w/w). The yield of ethanolysis of PKO with the ratio of 1.4 (w/w) is better than with the ratio of 1.0 (w/w) and 1.2 (w/w), while 6 minutes shown a better result for the PKO ethanolysis time reaction compared to 3, 9, or 12 minutes. The average of glycerides, esters, monoglycerides, internal standard, diglycerides, and triglycerides in overall treatments, shows 6.09, 55.02, 7.07, 2.55, 23.54, and 5.73%, respectively. Group of monoglyceride (MG) and diglyceride (DG) compounds in PKO ethanolysis products, both obtained on average with the best treatment at ethanolysis time for 3 minutes for a ratio of 1.0 (w/w), each at 7.74% (w/w) and 30.60% (w/w).

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<abstract> <p>The aim of the research was to study the effect of inoculum type and fermentation time on microbial growth patterns (yeast, fungi and bacteria), β-glucan formation and antioxidant activity during soybean fermentation into tempe. The research was conducted using factorial Completely Randomized Block Design with 3 replications. The first factor was the types of inoculum: commercial inoculum of tempe, Raprima (3%), a single inoculum of <italic>S. cerevisiae</italic> (3%), a single inoculum of <italic>R.</italic> <italic>oligosporus</italic> (3%), and mixed inoculum of 1.5% <italic>S. cerevisiae</italic> and 1.5% <italic>R. oligosporus</italic>. The second factor was the length of fermentation which consisted of 0, 8, 16, 24, 32 and 40 hours at room temperature. Regarding the number of fungi, yeasts and bacteria, the observational data were presented descriptively in the form of graphs, while for the data from the analysis of β-glucan and antioxidant activity, the data obtained were analyzed for variance with analysis of variance (ANOVA) and then analyzed further by the Least Significant Difference (LSD) at the 5% significance level. The results showed that the type of inoculum and duration of fermentation had an effect on increasing the growth of fungi, yeasts and bacteria, as well as increasing β-glucan content and the antioxidant activity of tempe<italic>.</italic> Yeast growth had a more dominant effect on increasing β-glucan content and antioxidant activity compared to fungi and bacteria. Tempe inoculated with a mixed inoculum of 1.5% <italic>R.</italic> <italic>oligosporus</italic> + 1.5% <italic>S. cerevisiae</italic>, resulted in the highest β-glucan content of 0.58% and the highest antioxidant activity at 82.42%. In conclusion, a mixed inoculum of 1.5% <italic>R. oligosporus</italic> + 1.5% <italic>S.</italic> <italic>cerevisiae</italic> with 36−40 hours of fermentation produced tempe with the highest β-glucan content and antioxidant activity. Therefore, the β-glucan content causes tempe to have better potential health benefits than tempe without the addition of <italic>S. cerevisiae</italic>.</p> </abstract>