Investigating the Potential Effects of Bacillus Subtilis Isolated from Moromi for Accelerating Soy Sauce Fermentation

Abstract

Soy sauce is a liquid condiment that is made from fermented soybeans with mold, wheat flour, brine water, bacteria, and yeast. Soy sauce fermentation includes two stages of fermentation which begins with koji fermentation and ends with moromi fermentation. Koji fermentation is a solid- state fermentation through the use of mold and it may last for 48 to 72 hours. Meanwhile, moromi fermentation is a submerged fermentation through the help of bacteria and yeast that may last from 3 months to 4 years. The long duration of the moromi fermentation is attributed to the high salt content, fluctuating fermentation temperature, and antagonistic relationships between microorganisms in the moromi. This is one of the problems due to the loss it caused in the soy sauce industry. There have been various studies regarding the acceleration of the moromi fermentation however the use of microorganism inoculation is still one of the most used methods. Bacillus spp. are one of the most predominant bacteria found in moromi fermentation. Bacillus subtilis, especially, has potential to accelerate the moromi fermentation by producing several important enzymes that will break down the substrates much faster. Therefore, this study aimed to investigate the potential effects of using B. subtilis as inoculum starter culture to accelerate the fermentation of soy sauce. There were two types of moromi samples in this study which were the control and the B. subtilis addition (BS). Both moromi underwent 4 weeks of fermentation at ambient temperature. After 4 weeks of fermentation, physicochemical analyses such as pH, total titratable acidity (TTA), total reducing sugar (TRS), and free amino nitrogen (FAN) were performed. There were significant differences (p<0.05) between control and BS on TTA, TRS, and FAN at week 2, week 0, and week 1 respectively. However, there were no significant differences (p>0.05) for each of the analyses after week 2. There were various factors that might cause these results such as high salinity, antagonistic relationship between microorganisms, and enzyme denaturation.