Continuous cultivation of Lactobacillus brevis NCL912 for production of gamma-aminobutyric acid

A continuous cultivation method for Lactobacillus brevis NCL912 to synthesize gamma-aminobutyric acid was developed in this work. Different dilution rates were evaluated for obtaining steady state in continuous cultivation. The results showed that steady state could be achieved at dilution rates from 0.08 to 0.12 h−1. The highest gamma-aminobutyric acid productivity (5.11 g L−1 h−1) was obtained at dilution rate of 0.09 h−1. The kinetic models were established for continuous gamma-aminobutyric acid production by using the Monod equation for microbial growth, and the Luedeking–Piret equation for product formation. The microbial growth and product formation can be described by equations \( \mu = {{{0.1234{C_S}}} \left/ {{\left( {0.9338+{C_S}} \right)}} \right.} \) and \( {Q_P}=6.86\,\mathrm{g}\,{{\mathrm{g}}^{-1 }}\mathrm{cell}\,{{\mathrm{h}}^{-1 }} \), respectively. The production of gamma-aminobutyric acid by L. brevis NCL912 was non-growth-associated.