Optimization of fermentive production of γ-aminobutyric acid (GABA) with nitrogen-rich waste feedstocks by selected microorganisms

• Main Authors: Shih-Ting Lin, 林思廷
• Other Authors: John Chi-Wei Lan
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/ten7u8

碩士 === 元智大學 === 化學工程與材料科學學系 === 106 === Currently, the potential antihypertensive effects of γ-aminobutyric acid (GABA) has been studied comprehensively. GABA plays a significant role in mediating clinically relevant actions of anesthetic agents. It is a type of amino acids which converted from glutamic acid, and involves in the inhibition of brain activity that resulted in relaxing and sedating effects. The current medical research found that GABA is the major inhibitory neurotransmitter compound in the central nervous system. Nowadays, people are easily to have physical and mental discomforts due to their stressful and depressed lifestyle. Therefore, they tend to rely on tranquilizers and sleeping pills for pain relieve. There are many commercially available tranquilizers and sleeping pills in the market, but not all are safe-to-use and might have side effects if over dosage. However, tranquilizers and sleeping pills that contain GABA are recognized as the most stable and safe-to-use drugs to achieve a physical and mental state of peace and relaxation. In this study, five bacteria strains from fermented food, i.e., Bacillus subtills BBEL02, Lactobacillu Rhamnosus GG, Lactobacillus plantanm, Bacillus BEL03 and Weissella cibaria rain CMS2 BBEL04 were self-screened. Their GABA production was first investigated with MRS medium supplemented with 3% (w/v) sodium glutamate (MSG). Our observations revealed that Bacillus subtills BBEL02 and Weissella cibaria rain CMS2 BBEL04 showed higher GABA productivity among the others. They yielded 101.3 and 33.4 mgg-1d-1 GABA, respectively, and their dry cell weight were 22.8 and 6.6 gL-1, respectively. Overall, Bacillus subtills BBEL02 was chosen for further studies. In the second part of the experiment, different culture medium formulations were studied for GABA production. The basal medium with addition of different carbon sources (i.e., glucose, galactose, mannose and sucrose) and different carbon source concentrations (i.e., 1%, 3% and 5% (w/v)) were optimized. Our results inferred that supplementation of 1% of glucose to the basal medium achieved the highest yield of GABA (347.3 mgg-1d-1), As a result, 1% (w/v) of glucose was used as the carbon source in this experiment. Subsequently, the alternative nitrogen sources and additional glutamic acid were supplemented to investigate the synthesis of GABA. The highest GABA accumulation (10.94 gL) was obtained by adding 5% (w/v) to 2% (v/v) soybean hydrolyzed liquid. Lastly, a flask system on the yeast cell culture was carried out to study cell expansion. The highest cumulative yeast amount of 22.7 g and the yield of 4.95 gL-1d-1 were successfully obtained, which are comparable to the literature and has great potential.