Over 2000-Fold Increased Production of the Leaderless Bacteriocin Garvicin KS by Increasing Gene Dose and Optimization of Culture Conditions.

Amar A Telke,Tage Thorstensen,Geir Mathiesen,Dzung B Diep,Kiira S Vuoristo,Kirill V Ovchinnikov

doi:10.3389/fmicb.2019.00389

Amar A Telke, Tage Thorstensen + Show 4 more

Open Access

https://doi.org/10.3389/fmicb.2019.00389

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Abstract

The leaderless bacteriocin Garvicin KS (GarKS) is a potent antimicrobial, being active against a wide range of important pathogens. GarKS production by the native producer Lactococcus garvieae KS1546 is, however, relatively low (80 BU/ml) under standard laboratory growth conditions (batch culture in GM17 at 30°C). To improve the production, we systematically evaluated the impact of different media and media components on bacteriocin production. Based on the outcomes, a new medium formulation was made that increased GarKS production about 60-fold compared to that achieved in GM17. The new medium was composed of pasteurized milk and tryptone (PM-T). GarKS production was increased further 4-fold (i.e., to 20,000 BU/ml) by increasing the gene dose of the bacteriocin gene cluster (gak) in the native producer. Finally, a combination of the newly composed medium (PM-T), an increased gene dose and cultivation at a constant pH 6 and a 50–60% dissolved oxygen level in growth medium, gave rise to a GarKS production of 164,000 BU/ml. This high production, which is about 2000-fold higher compared to that initially achieved in GM17, corresponds to a GarKS production of 1.2 g/L. To our knowledge, this is one of the highest bacteriocin production reported hitherto.

Highlights

The decreasing effectiveness of antibiotics has become a serious worldwide problem due to the emergence of multidrug-resistant bacteria (Bush et al, 2011; Laxminarayan et al, 2016)
Two different ways were used to describe the production of garvicin KS in a culture: production per ml expressed as bacteriocin unit per ml (BU/ml), and production per 108 cells expressed as BU/108 cells, the latter being referred to as specific production
As for many other bacteriocins, Garvicin KS (GarKS) is produced at relatively low levels under normal laboratory growth conditions (Ovchinnikov et al, 2016)

Summary

Introduction

The decreasing effectiveness of antibiotics has become a serious worldwide problem due to the emergence of multidrug-resistant bacteria (Bush et al, 2011; Laxminarayan et al, 2016). Most bacteriocins are membrane-active peptides, killing sensitive bacteria by membrane disruption after selective interaction with specific membrane receptors (Oscariz and Pisabarro, 2001; Hasper et al, 2006; Diep et al, 2007; Nissen-Meyer et al, 2009; Tymoszewska et al, 2017). This mode of action is different from most antibiotics, which often act as enzyme-inhibitors (Davis, 1987; Bush and Jacoby, 2010). Various heterologous expression systems have been reported for increased bacteriocin production (Horn et al, 2004; Kong and Lu, 2014; Jimenez et al, 2015; Jiang et al, 2016; Mesa-Pereira et al, 2017)

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