Journal of Food, Agriculture and Environment

Production of L-lysine by Brevibacterium lactofermentum and its application in eco-friendly synthesis of gold nanoparticles using gamma radiation

Author(s):

Ahmed I. El-Batal ¹, Roquia Al-Habib ²

Recieved Date: 2014-01-11, Accepted Date: 2014-04-02

Abstract:

The target of the present investigation was to optimise the modified fermentation medium composition (different carbon, nitrogen and mineral sources) for L-lysine production by Brevibacterium lactofermentum mutant strain in submerged fermentation. Also, the two factors affected L-lysine production, such as biotin as a metabolic activator and L-alanine as a metabolic regulator, were studied to increase the rate of production. The most effective components for L-lysine biosynthesis were selected and the optimal concentrations of these components were determined under the optimised conditions and modified fermentation medium of (20% molasses as a carbon source, 3% ammonium sulphate, 3% CaCO₃ , 400 µg l^-1 biotin and 75 mg% L-alanine) with maximum L-lysine (40.6 g l^-1) yield. Stimulatory effect in L-lysine production was observed when low concentrations of some surface active agents as membrane and cell wall permeability enhancers of Tween (20, 40, 60 and 80) and Triton X-100, as well as organic solvent dimethylsulfoxide (DMSO) were added at various concentrations during the process of fermentation. The addition of Tween-60 (0.1%, v/v) after 10 h of cultivation gave the highest L-lysine yield (50.0 g l^-1) after 4 days of incubation time under the optimised conditions of the modified fermentation medium. L-lysine aqueous solution, which was used as reducing and stabilising agent, stimulated eco-friendly synthesis of gold nanoparticles (AuNPs) using radiolytic reactions of gamma radiation. The incorporation of L-lysine with AuNPs was confirmed by UV-visible, dynamic light scattering (DLS), Fourier Transform infra red (FT-IR) and spectrophotometers. Also, transmission electron microscope (TEM) analysis revealed morphology of well dispersed spherical AuNPs with size ranging from 6.79 nm to 9.54 nm with mean diameter of 8.73 nm.

Keywords:

L-lysine, Brevibacterium lactofermentum mutant strain, submerged fermentation, surface active agents, gold nanoparticles, gamma radiation

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Journal: Journal of Food, Agriculture and Environment
Year: 2014
Volume: 12
Issue: 2
Category: Food and Health
Pages: 141-149

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