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The present work analyzes the effect of incorporating a lipolytic enzyme (Lipolase ® 100L) into detergent formulas for washing fatty soils on hard surfaces. The experimental device, which is called a "bath-substrate-flow" device, uses a continuous flow on a substrate (glass spheres) soiled with triolein. Washing tests were done using only the enzyme and changing both its concentration and the temperature of the process. The results showed that, in the presence of lipase, soil removal was achieved through three consecutive mechanisms: (i) fundamental removal of the soil by the bath flow through the experimental device; (ii) emulsion of the soil in the washing medium; and (iii) enzymatic hydrolysis of the dispersed soil. Different commercial surfactants were used, and detergency was evaluated in the absence and presence of lipase. The use of surfactant formulas with the lipolytic enzyme showed a positive effect of the enzyme on the detergency values registered with the fatty alcohol ethoxylate surfactants Findet ® 10/15 and Findet 1214N/23, and with the anionic surfactant linear alkylbenzene sulfonate. The commercial surfactants Glucopon ® 600, Glucopon 650, Findet 10/18, and Findet Q/21.5NF alone each presented high detergency values for fatty soils, and the effect of the incorporation of the lipase was not significant.Paper no. S1493 in JSD 9, 83-90 (Qtr. 1, 2006).

The toxicity values of fatty-alcohol ethoxylates, nonylphenol polyethoxylate, and alkylpolyglucosides have been determined by applying assays with luminescent bacteria. Also, the relation between metabolites and ecotoxicity during the biodegradation process has been determined. The biodegradation tests were carried out according to the OECD 301 E test for ready biodegradability. In these tests a solution of the surfactant, representing the sole carbon source for the microorganisms, was tested in a mineral medium, inoculated and incubated under aerobic conditions in the dark. The toxicity of surfactants is related to their molecular structure (Quantitative Structure Activity Relationships, QSAR). For the alkylpolyglucosides, toxicity expressed as EC(50) is related with the critical micelle concentration (CMC), the hydrophilic-lipophilic balance (HLB) of the surfactant, and the hydrophobic alkyl chain (R). The results indicate that toxicity increased as the CMC decreased and as the hydrophobicity increased and R rose. For fatty-alcohol ethoxylates, parameters characteristic studied have been HLB, number of units of ethylene oxide and the alkyl chain length. Relationships found are in agreement with the fact that increasing the alkyl chain length leads to a lower EC(50), whereas increasing ethoxylation leads to a lower toxicity. An analysis of the behaviour of the toxicity and HLB again indicates that the toxicity was greater for surfactants with a smaller HLB. The evolution of the toxicity was studied over the biodegradation process, expressed as a percentage of inhibition. For all the non-ionic surfactants assayed, except for the nonylphenol polyethoxylate, a major decline was found in toxicity during the first days of the biodegradation assay and at all the concentrations tested.

This paper concerns the primary biodegradation of different commercial fatty-alcohol ethoxylate surfactants (FAEs), applying the OECD 301 E test for ready biodegradability. Changes were made both in the carbonchain length of the surfactants as well as in the number of units of ethylene oxide (EO) in its molecule. The biodegradation were monitored, analysing the colony-forming units (CFU) formed during this process. From the biodegradation profiles drawn for the FAEs, parameters characteristic of the biodegradation process were defined: latency time (t L ), biodegradability at 50 h of assay (B), half-life (t 1/2 ), mean biodegradation rate until reaching biodegradability of 85% (V M ), and the residual concentration of the surfactant (S R ). The analysis of these parameters enabled the establishment of the influence of surfactant concentration and structure during the biodegradation process. The increase in the surfactant concentration lowered the rate of the biodegradation process and the biodegradability of the surfactant in addition to the half-life and residual concentration of the surfactant. The mean biodegradation rate, V M , for fatty-alcohol ethoxylates increased with the number of EO units and molecular weight of the surfactant. At low initial test concentrations (less than 25 mg/L), the concentration of the residual surfactant rapidly diminished with biodegradation time. For higher concentrations, after an adaptation period of the microorganisms, the surfactant concentration declined exponentially and the biodegradation rate became far slower for all the surfactants. The parameters characteristic of the growth curves: specific growth-rate, k, and the yield of biomass production per gram of surfactant, Y ap , made possible the quantification and corroboration of the results during the biodegradation process.