1 Plant Archives Vol. 20, Supplement 2, 2020 pp. 3183-3191 e-ISSN:2581-6063 (online), ISSN:0972-5210 BIOREACTOR STRATEGIES TO INCREASE THE ENGINEERED PROTEIN PRODUCTION IN LACTOCOCCUS LACTIS Pranav Kumar Prabhakar Department of Transdisciplinary Research, Lovely Professional University, Phagwara Punjab India *corresponding Author: Email: pranav.16113@lpu.co.in Abstract Lactococcus lactis is a lactic acid bacterium widely used in various food and fermentation processes. L. lactis is one of the organism which is treated as generally regarded as safe (GRAS) organisms, whichch is used for as genetic machinery for the genetic and chromosomal engineering and vectors to facilitate cloning and gene expression and produces a number of important proteins. However, the production of large quantities of biologically active recombinant proteins in this organism is restricted due to a number of factorsand biological constraints. One of the constraints with this system is that, in glucose growing culture, L. lactis develops a stress response and cessation of growth due to the acidification of medium. Prior work in our laboratory has shown that suppression of this response increases the streptokinase productivity in L.lactis. It was shown that buffering the medium suppresses development. In this work, the correlation between ATR suppression and increase in recombinant protein activity was used to develop bioreactor strategies for enhancement of volumetric activity of recombinant streptokinase. Keywords : Lactic acid, lactobacillus, fermentation, recombinant, streptokinase. Introduction Advancements in genetic engineering and bioprocess technology have seen the development of several potent expression systems for production of recombinant proteins. These recombinant proteins have wide applications in therapy, diagnostics and industrial processes (Kar et al., 2016; Farooq and Sehgal, 2019a, 2019b). These expression systems include Gram-positive and Gram negative prokaryotes, yeasts, filamentous fungi, plant cell, insect cell and mammalian cell cultures as well as in-vitro expression. All the expression systems employed so far have certain advantages as well as disadvantages that should be considered during their selection (Rai et al., 2001; Singh and Das, 2017). An effective process for the production of recombinant proteins is characterized by increased product as well as biomass (Riesenberg and Guthke, 1999; Chouhan, et al., 2017; Malkania et al., 2018). Among the several expression systems available, bacterial expression systems are more amenable to the condition of high specific- productivity, concomitant with high cell concentrations in fermentation processes. Therefore, they have been widely used on the industrial scale for the production high value recombinant proteins (Singh et al., 2016; Singh and Thakur, 2018; Singh et al., 2019). The design of prokaryotic expression vectors has been extensively investigated (Makrides, 1996) and various essential features of the expression vector has been identified and optimized for better performance (Malik et al., 2013; Kaur et al., 2016; Malik et al., 2016). The selection of the expression systems also depends on the properties of the recombinant protein to be over-expressed. Even though optimized expression strains and vectors are available for all expression systems developed there is a lack of universally- employed host-vector system for high-level expression of heterologous proteins (Kumar et al., 2019; Kaur et al., 2020; Prabhakar et al., 2020). A lactic acid bacterium, Lactococcus lactis is used very frequently in the food processing industries for making cheese, buttermilk, as preservative, for probiotics etc (Mishra et al., 2018; Mishra, 2019a, 2019b). L. lactis is one of the organism which is treated as generally regarded as safe (GRAS) organisms, whichch is used for as genetic machinery for the genetic and chromosomal engineering and vectors to facilitate cloning and gene expression and produces a number of important proteins (Sharma et al., 2017). However, the production of large quantities of biologically active recombinant proteins in this organism is restricted due to a number of factorsand biological constraints (Le Loir et al., 2005). Recombinant proteins can be synthesized and targeted to different compartments in L. lactis (Table-1) (Nauta et al., 1996; O’Sullivan et al. 1996; Sanders et al., 1997, 1998; Kuipers et al., 1998).