Detection of a whitening fluorescent agent as an indicator of white paper biodegradation: a new approach to study the kinetics of cellulose hydrolysis by mixed cultures.
A simple and reliable method to estimate paper degradation by cellulolytic bacteria is described. This method is based on the detection in the culture medium of a fluorescent whitening agent (FWA) added to white paper during the manufacturing process. Preliminary results using a Cellulomonas strain cultivated in a liquid medium containing FWA, indicated that this component is non-toxic at a final concentration of 0.01 per thousand (v/v) and that the fluorescence decreased during the first 24 h of incubation, i.e. during exponential growth phase, suggesting an adsorption of FWA on bacterial cells. Consequently, all experiments have been performed with a liquid medium containing FWA (0.01 per thousand v/v) and white paper (8.0 g/l) as cellulose source. Mixed bacterial populations (MBPs) were prepared from refuse samples. These MBPs, which mainly consisted of bacterial rod cells, were used as inocula and fluorescence was measured after 30 h of incubation, i.e. after the stationary phase was reached. A high linear correlation (R(2) = 0.979) was found between the percentages of degraded paper (%P) deduced from residual paper weight and the fluorescence values (F) of the culture medium and the following equation between %P and F was determined: %P = 8.71x10(-5) x F. An additional experiment using a second MBP showed a strong correlation (R(2) = 0.990) between the measured %P and the %P estimated from F values, confirming the reproducibility of the method. Moreover, the time course of paper degradation by five replicate flasks from a unique MBP was set up. Paper degradation was detected 3 to 5 days after the beginning of the stationary phase. The average degradation rate between the 7th and the 11th day of incubation was 11.4% per day. Rates of paper degradation ranged from 31 to 60% after 10 days and from 77 to 88% after 3 weeks of incubation, depending on the inoculum.
Bichet-Hébé
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Laboratoire des Sciences de l'Environnement et de l'Aménagement, Faculté des Sciences, Angers, France.
Pourcher
A M
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Sutra
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L
Comel
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C
Moguedet
G
G
D001673:Biodegradation, Environmental; D002482:Cellulose / Q000378:metabolism*; D005456:Fluorescent Dyes; D006093:Gram-Positive Asporogenous Rods / Q000378:metabolism*; D006868:Hydrolysis; D010209:Paper; D013997:Time Factors
D005456:Fluorescent Dyes; D002482:Cellulose