The effects of incubation temperature and pH on Exopolysaccharides production by Lactic acid bacteria

• Main Authors: Cheng-Ju Yang, 楊政儒
• Other Authors: Tung-Yung Lin, Ph. D.
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/06098863031187273203

碩士 === 中國文化大學 === 生活應用科學研究所 === 93 === Abstract The aim of this research was to determine the yield and examine the properties of exopolysaccharides (EPS) produced by Lactobacillus helveticus CCRC14030. L. helveticus CCRC14030 was inoculated in skim milk medium and incubated in a fermentor at 25, 37, and 50℃, pH 5, 6, and 7 for 0-108 h. The fermented samples were withdrawn at intervals of 48, 72, 96 and 108 h for determinations of viscosity, total viable counts, EPS yield, ropy condition, monomer, molar mass, and times of subculture on viscosity. The viscosities of fermented samples ranged from 1.54 to 5.88 cp were not significant different (P>0.05) among incubation times. The highest viscosity was observed in the fermented sample of pH 5 among three pHs and 25 and 50℃ were found to be the better incubation temperatures for improving the viscosity. The viscosity of the fermented samples after 48 h of incubation decreased due to increase in total viable counts at 24 h. Higher viable counts resulted in the decrease in the amount of casein in the skim milk medium and the viscosity. The highest total counts of L. helveticus CCRC14030 was observed at 72 h of incubation. The viable counts decreased after 96 and 108 h. Although EPS yields were not significant different (P>0.05) among incubation times, the highest EPS yields of 1.79-2.81 g/L were found in the incubation condition of 25℃, pH6 and 48-108 h. The highest ropiness values were observed in the EPS produced by L. helveticus CCRC14030 incubated at 25℃, pH6 for 96 and 108 h, and the values were 4.78 and 5.86 cm, respectively. Galactose was found in EPS produced by most of L. helveticus CCRC14030 treatments, and the content was in the descending order by glucose, N-acetyl-glucosamine, and rhamnose. The content of rhamnose was the lowest. The different content of each monomer was found at different inoculated condition. Two fragments of different molar mass found in EPS were 347~324168 and 3.309~84.733 kDa, respectively and the contents were 35~100% and 7~100%. The highest ropiness value of EPS produced by L. helveticus CCRC14030 was inoculated at 25℃, pH 6, it was 1636 kDa. The non-ropy EPS produced by L. helveticus CCRC14030 was inoculated at 37、50 ℃, pH 6, they were also high molar mass, about 103029~202752 kDa, occupied in 35~100%. L. helveticus CCRC14030 with different subculture times of was inoculated at 25 ℃, pH 5. The highest total viable counts of the culture strain with 15 subculture times was 6.95x108 CFU/mL, which was lower than 3.29x109 CFU/mL of the culture strain with 7 subculture times.The EPS yield of the culture strain with different subculture times produced ranged from 0.17 to 0.34 g/L. Camparing the EPS ropiness value , the ropiness value of EPS produced by all fermented times except 48 h of the culture strain with 7 subculture times were better. The ropiness value of EPS produced by 48 and 108 h fermented times of the culture strain with 15 subculture times were significant different (P＜0.05), others were not significant different (P>0.05). The monomer of the culture strain with different subculture times contained rhamnose, N-aceyl-glucosamine, galactose and glucose, which was different from the fermented times and also varied the composion of monomer. The molar mass of EPS and it's proportion of the culture strain with 7 subculture times were high molar mass EPS, the molar mass of EPS produced by the culture strain with 15 subculture times were low molar mass EPS. In conclusion, L. helveticus CCRC14030 was the ropy strains. It was inoculated in fermentor filled with skim milk at 25 ℃, pH 6, after 96 h which produced the EPS yield and it's ropy condition of this condition were the best. KEYWORD：Exopolysaccharides, Lactic acid bacteria.