Isolation, Characterization, and Identification of Microorganism from Bali Traditional Soy Sauce for The Production of Low sodium Soy Sauce

Abstract

Soy sauce is a popular food condiment in Asia that is made of soybean, wheat, and salt through a two-step fermentation process. The first step is a solid-state fermentation to produce koji by adding mold spores, typically Aspergillus species, to the mixture of soybean and wheat. The second stage is a brine fermentation or moromi, which is done by immersing the koji in brine water (18-22% NaCl) and left to ferment for 3-6 months. Fermented koji serves as the source of hydrolytic enzymes, including protease, amylase, and lipase, that break down protein, carbohydrate, and lipid, respectively, into smaller components. These smaller components are important to the final attributes of soy sauce as well as serve as nutrients for halophilic microbes that grow during moromi fermentation. These microbes are important to the flavor development and grow optimally at high salt concentration. Unfortunately, such high salt concentration can contribute to high salt intake which has been linked to many cardiovascular diseases. At the same time, reducing the concentration of salt during moromi fermentation can alter the microbial growth and composition, and therefore the quality of soy sauce. This study explored potential soy sauce fermenting microbes for use in low salt soy sauce without compromising its quality. The study was done by isolating and characterizing the dominant microbes, screening their enzymatic activities, and identifying the potential microbes, which were obtained from koji and moromi samples collected from a traditional soy sauce factory in Bali. There were 20 isolates identified consisting of 4 yeasts, 7 molds and 9 bacteria. The majority of isolates showed positive results for protease, amylase, and lipase at 5% NaCl, indicating their potential to be used as starter cultures for low salt moromi fermentation. Therefore, 20 out of 26 isolates only maintain the enzymatic activities when grown in 5% low salt condition and no enzymatic activities in 20% salt condition. The obtained isolates can be further studied for its potential in a low salt moromi fermentation.