Preliminary study on seaweed fermentation for lactic acid production

Abstract

Indonesia is a maritime country that is rich in seaweed. However, seaweed fermentation into lactic acid is not yet usually. Seaweed fermentation has outstanding potential because it has the most abundant polysaccharides compared to other sources. This research aims to synthesize lactic acid by fermentation using a single culture of Lactobacillus plantarum (L. plantarum) and two substrates, namely seaweed flour and refined salt Kappa-Carrageenan (RKC). Lactic acid was analyzed by fourier-transform infrared (FT-IR) spectroscopy and its concentration was determined by gas chromatography-mass spectrometry (GC-MS). The proximate analysis showed that crude Fiber and starch levels in seaweed are 25.37% and 14.66% (w/w) and also in RKC are 16.45% and 1.07% (w/w), respectively. The highest reducing sugar was attained at H2SO4 2% (w/w), which were 51,184 mg/L in RKC and 24,824 mg/L in seaweed flour. Based on FT-IR data, lactic acid characteristic signals were found at broadband approximately 3000 - 3500 cm−1, which indicated the presence of OH band, a band at 1656 cm−1 revealed C=O stretching of carbonyl groups, and a band at 1118 cm−1 for C-O stretching of alcohol. Based on GC-MS data, the highest lactic acid production was 42,267 mg/L in RKC and 37,130 mg/L in seaweed flour. In this study, we can conclude that the efficiency of hydrolysis and fermentation of RKC was better than seaweed flour. However, the substrate concentration for optimum lactic acid production was unknown, so a more in-depth study was needed.

The carrageenan fermentation process for (L)-lactic acid production using Lactobacillus plantarum: effect of fermentation time

“…Therefore, the current work suggests that RKC hydrolysate can be used as a substrate for the fermentation of L. plantarum. Based on the previous report, the sample of RKC that was used contained starch as a source of glucose [15], so the HPLC analysis of reducing sugars that were monitored during fermentation was (D)-glucose and (D)-galactose. The standards used to identify the peaks were (D)-glucose, (D)-galactose, and (L)lactic acid.…”

“…The raw material was commercial RKC purchased from the local market in West Java, Indonesia. The proximate analysis of RKC as a raw material has been carried out and presented in the previous report [15]. The lactic acid bacteria were pure cultures of Lactobacillus plantarum purchased from the local laboratory in West Java, Indonesia.…”

“…In the previous report, the optimum sulphuric acid concentration for RKC hydrolysis was H2SO4 2% (v/v) [15], so in this study, H2SO4 2% (v/v) was used as a catalyst for RKC (15 % w/v) hydrolysis. First, the sample in the Erlenmeyer flask was dissolved with H2SO4 2% (v/v).…”

“…Then, it was put into an autoclave and hydrolyzed at a temperature of 121 °C and a pressure of 1 atm for 45 minutes. Next, the hydrolysate was cooled, neutralized with 20% NaOH (v/v), and filtered by vacuum filtration [15,16]. The reducing sugar concentrations were determined by the Nelson-Somogyi method [17].…”

“…Some or all strains in Lactobacillus bulgaricus, Lactobacillus delbreckii, Lactobacillus lactis, and Lactobacillus brevis cannot produce lactic acid from galactose, while L. acidophilus and L. plantarum can [7,14]. Furthermore, our previous report showed that refined kappa-carrageenan (RKC) is a potential substrate of LA production using L. plantarum [15]. This study aimed to optimize the LA production by RKC as a galactose resource and L. plantarum as LAB by improving the method and adding a number of nutrients.…”