%0 Journal Article
%T Bleaching of biofilm-forming algae induced by UV-C treatment: a preliminary study on chlorophyll degradation and its optimization for an application on cultural heritage.
%A Pfendler S
%A Munch T
%A Bousta F
%A Alaoui-Sosse L
%A Aleya L
%A Alaoui-Sossé B
%J Environ Sci Pollut Res Int
%V 25
%N 14
%D May 2018
%M 29520550
%F 5.19
%R 10.1007/s11356-018-1654-6
%X Green microalgae colonizing stone surfaces represent a major problem for the conservation of heritage monuments, since they lead to biodegradation and aesthetic issues. Previous studies in La Glacière show cave (France) have demonstrated that UV-C may have a strong effect on microalgae, thus leading to chlorophyll bleaching, which was increased when biofilms were maintained under VIS-light condition unlike to those maintained in the dark. To understand the physiological mechanisms underlying this response and in order to optimize in situ treatment, 30 kJ m-2 UV-C exposure times were applied to Chlorophyta Chlorella sp. and chlorophyll degradation kinetics were then monitored. UV-C irradiation was enough to inhibit photosynthesis and to directly kill all algal cells. Results also showed that chlorophyll a was degraded faster than chlorophyll b and that 14 h were necessary for complete degradation of all the present chlorophyll. In addition, our results highlighted the importance of visible light exposition after UV-C treatment which leading to chlorophyll bleaching. Irradiated algae cultivated in the dark were still green 5 days after treatment while cultivated samples in the light lost their green color after 14 h. An efficient UV-C treatment applicable to show caves and other heritage monuments was proposed.