Hydrogel Film-Immobilized Lactobacillus brevis RK03 for γ-Aminobutyric Acid Production

Abstract

Hydrogels of 2-hydroxyethyl methacrylate/polyethylene glycol diacrylate (HEMA/PEGDA) have been extensively studied for their use in biomedical and pharmaceutical applications owing to their nontoxic and highly hydrophilic characteristics. Recently, cells immobilized by HEMA/PEGDA hydrogels have also been studied for enhanced production in fermentation. Hydrogel films of HEMA/PEGDA copolymer were generated by Ultraviolet (UV)-initiated photopolymerization. The hydrogel films were used to immobilize viable Lactobacillus brevis RK03 cells for the bioconversion of monosodium glutamate (MSG) to γ-aminobutyric acid (GABA). The mechanical properties and fermentation yields of the L. brevis RK03 cells immobilized on polyacrylate hydrogel films with different monomeric formulations were investigated. Fermentation was carried out in 75 mL de Man, Rogosa and Sharpe (MRS) medium containing various concentrations of MSG. We found that HEMA (93%)/PEGDA (3%) hydrogels (sample H) maximized GABA production. The conversion rate of MSG to GABA reached a maximum value of 98.4% after 240 h. Bioconversion activity gradually declined after 420 h to 83.8% after five cycles of semi-continuous fermentation. Our results suggest that HEMA (93%)/PEGDA (3%) hydrogels have great potential for use in GABA production via semi-continuous fermentation.

Metabolism Characteristics of Lactic Acid Bacteria and the Expanding Applications in Food Industry

“…Lactobacillus johnsonii (Mayer et al, 2020) Glucan will extend to the crumb porosity of bread Improvement of bread texture Limosilactobacillus reuteri (Leemhuis et al, 2014) (Continued) Levilactobacillus brevis (Lyu et al, 2019) Levilactobacillus brevis D17 (Gong et al, 2019) GadC transports L-glutamate into the cell Lactococcus lactis (Small and Waterman, 1998) Glutamate decarboxylase and pyridoxal-5 -phosphate participate in the decarboxylation reaction of L-glutamate Lactococcus lactis (Cui et al, 2020) The cell immobilization technology increase GABA production Levilactobacillus brevis RK03 (Hsueh et al, 2017) Levilactobacillus brevis (Shi et al, 2017) Flavor substances SHMT gene encodes a serine hydroxymethyltransferase with threonine aldolase activity Produce flavor substances (2,3-butanedione and 2,3-pentanedione, etc.) in wine, vinegar, bread, sourdough and cheese…”

“…Among them, Levilactobacillus brevis TCCC 13007 can convert the substrates L-glutamic acid and monosodium glutamate into GABA, and the final titer reaches 201.18 g/L, and the molar bioconversion ratio is 99.4% ( Shi et al, 2017 ). In addition, the cell immobilization technology also plays an important role in the optimization of GABA production ( Hsueh et al, 2017 ). In the food industry, some microorganisms with high safety that can produce GABA can be used in the production of functional health food ingredients.…”

Glutamate Decarboxylase from Lactic Acid Bacteria—A Key Enzyme in GABA Synthesis

“…Utilization of whole cells for the biocatalytic conversion of glutamate to GABA has some drawbacks including the conversion of GABA to succinic semialdehyde by the enzyme GABA transaminase (GABA-T), which is often found in bacteria and might decrease GABA yields during cultivation. To prolong and thereby increase GABA production, continuous cultivation [91], fed-batch fermentation [92] as well as immobilized cell technology [93][94][95] have been employed. All of these approaches effectively increased GABA productivity by improving cell viability resulting in extended periods of cultivation.…”

Characterization of a Potential Probiotic Lactobacillus brevis RK03 and Efficient Production of γ-Aminobutyric Acid in Batch Fermentation

“…In particular, LAB have garnered attention from the food industry because they are generally regarded as safe (GRAS) organisms for GABA production. Several GABA-producing LAB have been reported, including Lactobacillus fermentum [ 11 ], Lactobacillus futsaii [ 12 ], Lactobacillus brevis [ 3 , 13 , 14 , 15 , 16 , 17 , 18 ], Lactobacillus delbrueckii subsp. bulgaricus [ 19 ], Lactococcus lactis [ 20 ], Lactobacillus paracasei [ 21 ], Lactobacillus plantarum [ 22 ], and Lactobacillus senmaizukei [ 23 ].…”