Note: Linear alkylbenzenesulphonate (LAS) bioavailable to anaerobic bacteria as a source of sulphur

Linear alkylbenzenesulphonate (LAS) (Fig. 1) is, apart from soap, the dominant surfactant in detergents worldwide (about 2·5× 10 t year, Schulze 1996). Commercial LAS is a mixture of linear alkanes (C10 to C13) each subterminally substituted with a single (4-sulfophenyl) moiety, and this mixture is the synthetic chemical product whose biodegradation has been examined to the greatest extent by regulatory agencies from data supplied to them (Schöberl 1993). Nevertheless, the use of LAS has been criticized on the basis of its non-degradability under anoxic conditions (Painter and Mosey 1992; Denger et al. 1996), a point accentuated by the finding of LAS in the sediment of the Mississippi (Tabor and Barber II 1996) and the Rhine (Schöberl and Spilker 1996). However, evidence for the existence of anaerobic bacteria able to cleave the C-SO3 − bond in chemically nonreactive organosulphonates has been published recently (Chien et al. 1995; Denger et al. 1996; Denger and Cook 1997). It has now been shown that the C-SO3 − bond of LAS is subject to cleavage under anoxic conditions and that for the first time, anoxic desulphonation of arylsulphonates is found in Gram-negative bacteria.