ε-poly-l-lysine production in static and agitated cultures withdifferent operation modes

Biopolymers have expanded in the global industry over the past two decades, because of its usage areas, durability, and price. Most of the biopolymers can be collected and/or extracted from natural sources. However, some of them are produced by microorganisms. Homopolymers are polymeric molecules in which one type of chemical repeat unit or monomer is repeated many times. Homopolymers are the most difficult to produce and due to high cost. ε-Poly-L-Lysine (ε-PL) is a natural food preservative and high yield antimicrobial agent produced from a fermentation process using Streptomyces albulus. ε-PL is a homopolymer of L-lysine, one of the basic amino acids and is a lysine straight chain polymer. ε-PL contains 25-35 L-lysine monomer which is linked by ε-amino bond coupled with a ε-amine to L-lysine. In this study, it was aimed to compare ε-PL production using Streptomyces albulus under static and agitated cultures. Beyond that a different operation mode with 3 different strategies were studied. In semi-continuous operation mode experiments glucose feeding, pH control under sugar free media and glucose feeding with pH control strategies were studied. High Performance Liquid Chromatography (HPLC) was used for determination of ε-PL. Also, biomass, sugar, and nitrogen contents were followed by cell dry weight, sugar analysis based on DNS method, and Nessler's reagent, respectively. The antimicrobial activity of the produced ε-PL was tested. Based on results, it was found out that the production with agitation was more efficient than static one. According to the results of the study, the amount of ε-PL produced by agitated culture is 3 times higher than the static culture. According to semi-continuous operation mode results, glucose feeding strategies production result was 0.33g/L, in second strategy which was pH control with sugar free media, the production amount was 0.51g/L for the third strategy which was glucose feeding with pH control, the production amount was 0.45g/L at most. The novel result of the study is that production with static culture can be increased with different surface area/volume ratio.