Effect of TiO₂ Nanoparticles and UV Radiation on Extracellular Enzyme Activity of Intact Heterotrophic Biofilms

Abstract

When introduced into the aquatic environment, TiO2 NP are likely to settle from the water column, which results in increased exposure of benthic communities. Here, we show that the activity of two extracellular enzymes of intact heterotrophic biofilms, β-glucosidase (carbon-cycling) and l-leucin aminopeptidase (nitrogen-cycling), was reduced following exposure to surface functionalized TiO2 NP and UV radiation, depending on the particles' coating. This reduction was partially linked to ROS production. Alkaline phosphatase (phosphorus-cycling) activity was not affected, however in contrast, an alkaline phosphatase isolated from E. coli was strongly inhibited at lower concentrations of TiO2 NP than the intact biofilms. These results indicate that enzymes present in the biofilm matrix are partly protected against exposure to TiO2 NP and UV radiation. Impairment of extracellular enzymes which mediate the uptake of nutrients from water may affect ecosystem function.

Nanomaterials in the environment: Behavior, fate, bioavailability, and effects—An updated review

“…In an elaborate mesocosm study that explored the ecosystem effects of Ag NM exposure, Colman et al () found reduced levels of leucine aminopeptidase (responsible for nitrogen cycling) and alkaline phosphatase (phosphorus cycling) enzyme activity, which was closely linked to reduced microbial biomass. Exploring intact heterotrophic freshwater biofilms after exposure to differently functionalized TiO 2 NMs in the presence or absence of environmentally realistic UV radiation, Schug et al () found reduced activity of ß‐glucosidase (carbon cycling) and leucine aminopeptidase. Exploring other types of freshwater communities, Gil‐Allué et al () and Tlili et al (, ) demonstrated distinct impacts of Ag NMs on biochemical functions of the biofilms in periphyton and litter decomposers, respectively.…”

The Effect of Titanium Dioxide Nanoparticles on Salivary Alkaline Phosphatase Activity

“…Schug et al results [23] show that in intact heterotrophic biofilms, the alkaline phosphatase activity was not affected following exposure to surface functionalized TiO2 NPs and UV radiation. While, an alkaline phosphatase enzyme isolated from E. coli was powerfully inhibited at lower concentrations of titanium dioxide nanoparticles than the intact biofilms.…”

Scientific Basis for Regulatory Decision-Making of Nanomaterials Report on the Workshop, 20–21 January 2014, Center of Applied Ecotoxicology, Dübendorf

“…[9] Such particle specific effects are becoming increasingly known. For instance, titanium dioxide (TiO 2 ) nanomaterials can influence the functioning of microbial digestion enzymes in biofilms [10] and nano-cerium dioxide (CeO 2 ) influences the growth of rhizobium in soy. [11] Compared to toxicity, data on bioaccumulation is scarcer.…”