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 ( ) 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.

Rizal S, Kustyawati ME, Suharyono AS, Suyarto VA. 2022. Changes of nutritional composition of tempeh during fermentation with the addition of Saccharomyces cerevisiae. Biodiversitas 23: 1553-1559. This study aimed to determine the effect of the addition of Saccharomyces cerevisiae on changes in nutritional composition during tempeh fermentation. The study used a Completely Randomized Block Design with two treatments and two replications. The first treatment was the type of tempeh inoculum with 4 levels, namely 0.2% commercial inoculum (Raprima), 1% Rhizopus oligosporus inoculum, 1% S. cerevisiae inoculum, and a mixture of 1% R. oligosporus inoculum, and 1% S. cerevisiae inoculum. The second treatment was the length of fermentation with 4 levels, namely 0 hours, 15 hours, 30 hours, and 45 hours. Observation parameters include fat, protein, ash, moisture, carbohydrates, and ?-glucan content during fermentation of tempeh. The data obtained were analyzed statistically using the Barlett and Tukey test then continued with the ANOVA test and the Orthogonal Polynomial-Orthogonal Comparison (OP-OC) test at the 5% level. The results showed that the addition of S. cerevisiae as an inoculum in making tempeh had an effect on changes in nutritional content during tempeh fermentation. The fat content, ash content, and moisture content of tempeh increased during fermentation, while the fat content and carbohydrate content decreased. The addition of 1% S. cerevisiae to tempeh fermentation by 1% R. oligosporus at 45 hours of fermentation resulted in the best nutritional content of tempeh with 17.40% protein content, 8.23% fat content, 65.74% moisture content, 1.33 ash content, 7.30% carbohydrate content, and 0.13% ?-glucan content.

Rizal S, Murhadi, Kustyawati ME, Hasanudin U. 2020. Growth optimization of Saccharomyces cerevisiae and Rhizopus oligosporus during fermentation to produce tempeh with high β-glucan content. Biodiversitas 21: 2667-2673. Saccharomyces cerevisiae grows and produces β-glucan during fermentation in tempeh production. The content of β-glucan in tempeh is influenced by the growth of S. cerevisiae throughout fermentation. The purpose of this study was to determine the effects of different types and concentrations of carbon sources on yeast growth, fungi growth, and β-glucan content in tempeh inoculated using Rhizopus oligosporus and S. cerevisiae. This study used a Factorial Randomized Complete Block Design (RCBD) with two factors and three replications. The first factor was the types of carbon sources, tapioca and wheat flour; the second factor was the concentrations of carbon source, 0.0%, 2.5%, 5.0%, 7.5% and 10.0% (w/w). Tempeh produced was investigated for yeast number, fungi number, β-glucan content, and pH value. The obtained data were tested using Tukey's Honestly Significance Difference (HSD) test. The results showed that the addition of various types and concentrations of carbon source significantly influenced the increase in yeast number, fungi number, β-glucan content, and pH in tempeh. The growth of yeast, fungi, and β-glucan content increased along with the increment of carbon source concentration. The amounts of yeast, fungi, and β-glucans in tempeh added with tapioca were higher compared to tempeh with wheat flour. The addition of 10% tapioca produced the highest amount of yeast with 9.505 Log CFU/g and the highest β-glucan content with 0.707% (w/w).

Phase changes of carbon dioxide (supercritical or subcritical) depend on its proximity to a pressure of 7.35 MPa and temperature of 31.1°C. Carbon dioxide becomes supercritical and subcritical when it is above and slightly below its critical point, respectively. This study aims to determine the effect of high-pressure CO₂ treatments at a pressure of 900 psi, 950 psi (subcritical), and 1100 psi (supercritical) and at holding times of 5, 10, and 15 min on the quality parameters of white shrimp (Litopenaeus vannamei) and to determine the shelf life of white shrimp processed with the best treatment. The results showed that the interaction between pressure and holding time had a significant effect on cholesterol, protein, moisture content, and value, but pressure had a significant effect on carotene content. The best treatment was a supercritical CO₂ treatment at 1100 psi for 10 min, which was determined based on a significant reduction in the number of microorganisms and no significant changes in color, texture, and fat content were observed compared with control. The best treatment was applied to process shrimps, which were then stored at 4°C to evaluate the effectiveness of scCO₂ treatment on the shelf life. No significant changes were found in PV and lipid in treated and scCO₂-treated shrimps during storage, but the treatment significantly affected pH, TVBN, and microbial counts. Among the samples, there was no hedonic difference in all sensory attributes. Supercritical CO₂ treatment at 1100 psi for 10 min can be an alternative method for preservation of shrimps.

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 S. cerevisiae (3%), a single inoculum of R. oligosporus (3%), and mixed inoculum of 1.5% S. cerevisiae and 1.5% R. oligosporus. 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. 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% R. oligosporus + 1.5% S. cerevisiae, 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% R. oligosporus + 1.5% S. cerevisiae 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 S. cerevisiae.