Immobilization of Lactic acid bacteria for production of extracellular polysaccharides

Abstract

Lactic acid bacteria (LAB) can produce extracellular polysaccharides that can be used as thickeners, emulsifiers, and gels in foods. The immobilization technology can effectively simplify and improve the separation and regeneration of extracellular polysaccharides. In this study, six strains of LAB, including the extracellular polysaccharide-producing strain Lactobacillus plantarum, were screened. The different immobilized carriers of sodium alginate, agar, gelatin-glutaraldehyde, and carrageenan were assessed for fermentation by these six LAB. Different diameters of beads were selected, and the optimum culture temperature, carrier concentration, and inoculum volume were evaluated. The results showed that the agar-embedding method was the best immobilization method and the optimum process conditions were as follows: 3% inoculum of L. plantarum, 30 g/L of agar as immobilization carrier with a particle diameter of 1 cm, and fermentation at 37 °C for 24 h. Through orthogonal experiments, the maximum exopolysaccharide (EPS) yield obtained was 1489.9 mg/L.

Quorum Sensing as a Trigger That Improves Characteristics of Microbial Biocatalysts

“…The level of productivity of the main metabolites in the cells in biofilms is at a significantly higher level in comparison with free cells. The same general effect is observed in most cells artificially immobilized in a concentrated form ( Table 2 ) [ 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 ]. It should be noted that poorly concentrated cell samples did not give improved levels of accumulated products even in immobilized form compared to the same free cells [ 49 ].…”

“…It should be noted that poorly concentrated cell samples did not give improved levels of accumulated products even in immobilized form compared to the same free cells [ 49 ]. The influence of some carriers used for immobilization of cells in the QS-state and their low porosity created additional limitations for mass transfer to realize the advantages of QS; therefore, the yields of the products were comparable to those typical for free concentrated cells [ 57 , 58 ].…”

“…A significant increase in the biosynthesis [ 45 , 46 , 47 , 48 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ] or the achievement of a concentration comparable to that accumulated by free cells in highly concentrated suspensions, which are generally formed by the end of the logarithmic growth phase [ 49 , 57 , 58 ], was shown for various PS producers as a result of their immobilization. In addition, the use of different methods of immobilization (adsorption on an insoluble carrier [ 48 , 50 , 51 , 53 , 54 , 55 , 56 , 57 ] or inclusion in a gel matrix [ 45 , 46 , 47 , 49 , 52 , 58 ]) led to the transition of bacterial cells into the QS state because the procedure resulted in a high-density cell culture and in keeping the cells in this state. The immobilization of PS producers in gel matrix has long been considered impractical due to diffusion difficulties and hampered mass transfer, which limits cellular metabolism [ 38 ].…”

“…However, it should be noted that despite many examples of the fact that higher yields of many target PSs can be obtained as a result of the use of immobilized cells compared to concentrated suspension cultures [ 45 , 46 , 47 , 48 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ], there are examples of when such an effect is absent. In particular, this applies to PSs synthesized by lactic acid bacteria [ 57 , 58 ]. The production of PSs using six BCs in the form of lactic acid bacteria strains ( Lactobacillus bulgaricus, L. acidophilus, L. plantarum, L. casei, Streptococcus thermophilus , and Lactococcus lactis ) was investigated.…”

Physical and chemical properties, structural characterization and nutritional analysis of kefir yoghurt

“…Yoghurt gels with high whey protein ratio have a more discontinuous structure with larger pores, and the presence of large whey protein aggregates promotes the formation of coarse gel microstructures characterised by large gaps ( Krzeminski et al, 2011 ). There are research reports that yeast and acetic acid bacteria co-ferment and decompose proteins in the substrate to produce vitamin B6, consume oxygen in the system to produce anaerobic environment, and produce acetic acid to reduce the pH of the system, thereby activating some lactic acid bacteria to ferment lactose and produce extracellular polysaccharides ( Tao et al, 2022 ). In addition, The kefir group produces a cheese similar to the original kefir grains with increased acidity and more whey precipitation due to the synergistic action of multiple strains ( Karim and Aider, 2022 ).…”