Synthesis of Xanthan Gum fromXanthomonas campestrisImmobilized in Polyurethane

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 ].…”

“…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 ].…”

“…It should be noted that in the case of alginate producers ( A. vinelandii ) immobilized in a composite agar layer/microporous membrane, additional stimulation of PS synthesis was shown to increase by 2.7 times per 1 g of consumed substrate (sucrose) in comparison with concentrated suspension-free cells, also in the state of QS [ 49 ]. During the synthesis of xanthan by X. campestris cells immobilized on polyurethane foam, an increase in its biosynthesis by 267–274% was also observed [ 50 , 51 ].…”

“…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 ].…”

Advances on Bacterial and Fungal Biofilms for the Production of Added-Value Compounds

“…Additionally, Mesquita et al [ 99 ] studied the production of xanthan gum with Xanthomonas campestris immobilized in polyurethane, and evaluated the storage stability and capacity for recycling the immobilized cells. The volumetric xanthan productivity with immobilized cells (0.62 g·L −1 ·h −1 ) was higher than in suspended-growth culture (0.12 g·L −1 ·h −1 ), indicating that immobilization improved the production of xanthan gum.…”