Enhanced biodegradation of atrazine by bacteria encapsulated in organically modified silica gels

Biodegradation by cells encapsulated in silica gel is an economical and environmentally friendly method for the removal of toxic chemicals from the environment. In this study, recombinant E. coli expressing atrazine chlorohydrolase (AtzA) were encapsulated in organically modified silica (ORMOSIL) gels composed of TEOS, silica nanoparticles (SNPs), and either phenyltriethoxysilane (PTES) or methyltriethoxysilane (MTES). ORMOSIL gels adsorbed much higher amounts of atrazine than the hydrophilic TEOS gels. The highest amount of atrazine adsorbed by ORMOSIL gels was 48.91×10(-3)?mol/mlgel, compared to 8.71×10(-3)?mol/mlgel by the hydrophilic TEOS gels. Atrazine biodegradation rates were also higher in ORMOSIL gels than the TEOS gels, mainly due to co-localisation of the hydrophobic substrate at high concentrations in close proximity of the encapsulated bacteria. A direct correlation between atrazine adsorption and biodegradation was observed unless biodegradation decreased due to severe phase separation. The optimised PTES and MTES gels had atrazine biodegradation rates of 0.041±0.003 and 0.047±0.004?mol/ml gel, respectively. These rates were approximately 80% higher than that measured in the TEOS gel. This study showed for the first time that optimised hydrophobic gel material design can be used to enhance both removal and biodegradation of hydrophobic chemicals.

Authors: Benson JJ, Sakkos JK, Radian A, Wackett LP, Aksan A. ; Full Source: Journal of Colloid and Interface Science. 2017 Sep 11; 510:57-68. doi: 10.1016/j.jcis.2017.09.044. [Epub ahead of print]