Color measurements as a reliable method for estimating chlorophyll degradation to phaeopigments

Abstract

The application of biocides is a traditional method of controlling biodecay of outdoor cultural heritage. Chlorophyll degradation to phaeopigments is used to test the biocidal efficacy of the antimicrobial agents. In the present study, the usefulness of color measurements in estimating chlorophyll degradation was investigated. An aeroterrestrial stone biofilm-forming cyanobacterium of the genus Nostoc was chosen as test organism, comparing its different behaviour in both planktonic and biofilm mode of growth against the isothiazoline biocide Biotin T®. Changes in A(435 nm)/A(415 nm) and A(665 nm)/A(665a nm) and in the chlorophyll a and adenosine triphosphate (ATP) cell content were compared with the variations in the CIELAB color parameters (L*, a*, b*, C*(ab) and h(ab)). Our findings showed that both the phaeophytination indexes are useful in describing degradation of chlorophyl a to phaeopigments. Moreover, the CIELAB color parameters represented an effective tool in describing chlorophyll degradation. L* CIELAB parameter appeared to be the most informative parameter in describing the biocidal activity of Biotin T® against Nostoc sp. in both planktonic and biofilm mode of growth.

Efficacy of different chemical mixtures against green algal growth on limestone: A case study with Chlorella vulgaris

“…L * was the best parameter to determine the chlorophyll degradation in Nostoc sp. by a biocide, however a * was also well correlated with the phaeophytination indexes used to measure the chlorophyll degradation (Sanmartín et al, 2011). Db * was the most informative parameter in detecting greening (De Muynck et al, 2009;Sanmartín et al, 2012), as it turned yellow over time.…”

Improved Brilliant Blue G Staining of the Internal Limiting Membrane with Sharp Cut Filters of a Novel Viewing Filter System

“…In this study, we used CIELAB for evaluation of a color. The CIELAB is the most complete color space specified by the International Commission on Illumination, and is designed to approximate human vision and used for the comparative analysis of color in various fields [10,11,12,13,14]…”

Degradation of nitrocellulose-based paint by Desulfovibrio desulfuricans ATCC 13541

“…This sample, prepared in triplicate as described in "Nitrocellulose-based paint and paint sample preparation" subsection, was considered as the colour reference. Colour measurements were performed according to Sanmartin et al (2011), carrying out five measurements at random positions on an area of approximately 9.88 cm 2 (3.8 x 2.6 cm) of samples A and D, by use of a Konica Minolta colourimeter with a CR-300 measuring head (8-mm-diameter viewing area). The colour measurements were analysed by considering the CIELAB colour system (CIE 1986), which represents each colour by means of three scalar parameters or Cartesian coordinates: L*, lightness or luminosity of colour, which varies from 0 (absolute black) to 100 (absolute white); a*, associated with changes in redness-greenness (positive a* is red and negative a* is green); and b*, associated with changes in yellowness-blueness (positive b* is yellow and negative b* is blue).…”