Application of Lentikats Biotechnology for removal of nitrates from ion-exchange brines: Implications for adaptation of encapsulated denitrifiers

Abstract

Denitrifying Bacterium Paracoccus denitrificans encapsulated in polyvinyl alcohol matrix (so called Lentikats Biocatalyst; LB) was applied for the removal of nitrates from simulated ion-exchange brines (12.14 g.L^-1 Cl^-, 1.35 g.L^-1 SO₄^2-, and 2.26 g.L^-1 N-NO₃^-). The effect of brines dilution on the denitrification activity of fresh Lentikats Biocatalysts was tested simultaneously for four dilutions (100% = non-diluted, 80% = 4:1 brine:water, 60 and 40%) in four sequent repetitions per dilution without intermediate cultivation. In the first set, the denitrification of 100 and 80% brine was severely inhibited, while the denitrification activity in 60 and 40% brines was comparable to activity in non-inhibiting denitrification medium. The denitrification activity in 60 and 40% brines declined in later repetitions due to a lack of nutrients, while it increased in 80 and 100% brines before it declined as well. Such results are in contradiction to previous observations based on correlation analyses of data from longer experimental period. The detailed comparison implicates the adaptation of the encapsulated denitrification bacteria to higher salinity and emphasizes its importance for achievement of high denitrification activities of Lentikats Biocatalyst in industrial-scale applications even in non-diluted brines.

Key words: Denitrification, ion-exchange brines, Lentikats Biocatalyst, Paracoccus denitrificans, polyvinylalcohol.