The influence of pressure and temperature on the hydrolysis of prawn chitin in seawater by chitinase from serratia-marcescens

Ail other conditions being similar, the biochemical degradation of chitinolytic matrices in seawater was found take place to 1.8 times more rapidly in warm shallow waters than in deep cold waters. Oceanol. Acta, 1986, 9, 4, 515-517. RÉSUMÉ Influence de la pression et de la température sur l'hydrolyse de la chitine par la chitinase de Serratia marcescens Toutes les autres conditions étant identiques, l'hydrolyse enzymatique des matrices chitinolytiques est 1,8 fois plus rapide dans les eaux de surface que dans les eaux profondes et froides des océans. Oceanol. Acta, 1986, 9, 4, 515-517. The dissolution of carbonate shell debris is of great significance in the marine environment in relation to the oceanic carbon dioxide system through the capacity of seawater to buffer atmospheric co2 variations. Though a great amount of data is available on the solubility of carbonates (calcite, magnesian calcites, aragonite), including the effect of temperature and pressure (Mackenzie et al., 1983; Koch, Distèche, 1984; Koch, 1985), little is known about the real rate of degradation of biogenic shell debris under in situ conditions of pressure and temperature. Even when undersaturation in carbonate is reached in seawater, organic matrices (protein and chitin) coating carbonate crystals have to be destroyed before dissolution of the mineral phases can occur. The rate of this biochemical degradation by bacteria and perforating organisms will depend on pressure, temperature and other parameters (pH, 0 2 , etc.). Kim and ZoBell ( 1972), using staining techniques, have reported from static observations that the enzymatic hydrolysis of chitin was much greater at 25°C than at 4°C in seawater and that at neither temperature was the hydrolysis appreciably affected by increased pres0399-1784/86/04 515 03/S 3.30/<0 Gauthier-Villars 515 sure (up to 1000 bars), but no quantitative study of the reaction kinetics was made under pressure. This short note describes the temperature and pressure dependency of the enzymatic hydrolysis of chitin by chitinase in natural seawater. The seawater (pH~ 8.20} was collected off the coast of Calvi (Corsica) and filtered on Millipore 0.22 J.tm; it was not noticeably contaminated. Purified chitin from prawn carapaces was isolated following Jeuniaux (1963) and hydrolysed with commercial chitinase (0.02 g.ml) from Serratia marcescens. The enzymatic reaction was followed using a turbidimeter: the hydrolysis of chitin suspensions results in a decrease of turbidity as a function of time of hydrolysis. The high pressure equipment is that used for high pressure pH measurements, as described by Distèche (1974). In pressurized experiments, the change in turbidity is measured just after decompression. Figures 1 and 2 show the evolution of the hydrolysis reaction under three different conditions of pressure and temperature: 22°C and 1 bar, 22°C and 1 000 bars, 4°C and 1 bar. Both temperature and pressure influence the rate of the reaction. Chitin and chitinase are stable B. KOCH, A. DISTÈCH E