Linear alkylbenzene sulfonate (LAS) biodegrades easily and loses its tensioactive properties quickly through a primary biodegradation process, as many works of literature testify. Many studies have been carried out in laboratories or in pilot plants, whereas few have been undertaken in a wastewater treatment plant (WWTP). In Italy, unlike in other countries, no detailed investigation has been made so far to establish LAS biodegradation in real WWTP conditions. EniChem Augusta (EA) and Consorzio Po‐Sangone (CPS) have worked together for over two years on this problem, taking into consideration the large (flow rate: approximately 400 × 103 m3/d) and central active sludge WWTP of the metropolitan area of Torino, north of Italy. Specific LAS data have been obtained, using established HPLC techniques, in influent and effluent streams, in the dissolved (waters) and adsorbed (suspended solids and sludges) phases, to reach a complete mass balance. LAS removal >99% and LAS biodegradation of approximately 85% have been observed. Attention also has been given to LAS intermediates of biodegradation, namely the sulfophenyl carboxylates (SPC), using HPLC and GC‐MS techniques, the latter after derivatization. The SPCs have been found present only in the waters and not in the adsorbed phases (SS and sludges).

The unsaturated fatty acids contained in single-cell proteins prepared from Li 70 yeasts grown on methanol were studied in order to ascertain the position of unsaturation and the stereochemistry of the double bonds. The acids were extracted and esterified to the corresponding fatty acid methyl esters (FAMEs) as described in previous reports. The location of the double bonds was obtained by gas-chromatographicmass-spectrometric analysis of the trimethylsilyloxy derivatives of the FAMEs. The stereochemistry was deduced by nuclear magnetic resonance spectroscopy using an incremental addition study with Eu(fod), on FAMEs and on the corresponding epoxy derivatives. Three model FAME samples, methyl oleate (~c-C,,:,), methyl elaidate (9t-C18:,) and methyl linoleate (gc, 1 2 ~-C ~~: ~) , were compared. Most of the unsaturated fatty acids (about 74%) present in the single-cell proteins have structures identical with those known in animal lipids. The three most abundant unsaturated fatty acids display the following structure : ~C -C ~~: ~ (22.5y0), 9c-Cl8:, (19.4%) and 9 ~, 1 2 c -C , ~: ~ (29.2%). All double bonds possess a cis-configuration; the position of the double bond is a t C9-C10 for the monounsaturated acids and C9-C10 and C12-Cl3 for diunsaturated acids.