Microbial aspects of linear alkylbenzene sulfonate degradation in coastal water

Abstract

Viable and total bacteria were determined during linear alkylbenzene sulfonate (LAS) degradation in coastal seawater. Viable bacteria were determined by plate counts on marine agar media, while total bacteria were determined by flow cytometry after SYTO-13 staining. LAS degradation was monitored by high-performance liquid chromatography analysis. Seawater samples with LAS at 5 mg/L, incubated in the laboratory (20°C, 100 rpm, 30 d), showed in most cases a similar evolution in bacterioplankton abundance over time, characterized by three phases: (i) a progressive increase in bacterial density; (ii) a later decrease; and (iii) a fluctuating stationary phase. Bacterioplankton degraded the LAS by growing to populations with a high percentage of viable bacteria. The bacteria were rapidly grazed by protozoa, preventing anomalous high bacterial growth and ensuring the later channeling of LAS carbon to upper trophic levels.Paper no. S1154 in JSD 3, 303-308 (July 2000). KEY WORDS:Biodegradation, flow cytometry, LAS, marine bacteria, sea water, SYTO-13.Linear alkylbenzene sulfonate (LAS) is an anionic, biodegradable compound and one of the most widely used surfactants (1). Although LAS biodegradation has been frequently reported (2-5), studies on LAS biodegradation in the marine environment are relatively scarce (6-11). Coastal biodegradation data are of relevance, since littoral water is the final recipient of domestic and industrial wastewater. An understanding of the microbial and ecological basis of LAS degradation is important because of the volume and diversity of its usage and disposal. However, a deep understanding of LAS degradation processes in Nature is difficult, because enclosed experiments do not fully represent the marine reality, and pure bacterial cultures capable of LAS mineralization are lacking. This last situation suggests that LAS is predominantly biodegraded by a consortia of bacteria, as the reports of several groups affirm (12-15).The assessment of the impact of surfactants on coastal bacterioplankton is crucial because naturally occurring bacteria are the main (if not the only) agents responsible for the degradation and recycling of xenobiotics in Nature. However, studies of the effects of surfactants on naturally-occurring bacteria are scarce (16-20), mostly due to the lack of adequate techniques to study the changes in aquatic bacterial populations and their activities. A limiting step when studying LAS-degrading marine consortia is that most (>90%) marine bacteria are not cultivable in standard media (21,22), and so when a LAS-degrading consortium is used to isolate its individuals, some basic strains may be missed. It has already been reported that bacterial biomass produced when marine microorganism growth takes place at the expense of LAS is channeled to higher trophic levels by protozoa grazing (23,24). Protozoa, one of the most sensitive bioindicators of ecotoxicity in Nature, are more sensitive than bacteria, algae, invertebrates, and fish to the toxic effects of pollutants. Recent technol...

Biodegradation of Linear Alkylbenzene Sulfonates and Their Degradation Intermediates in Seawater

“…Nevertheless, although the aerobic biodegradation of LAS in seawater is evidently relevant, studies of this process are scarce (e.g., refs 6−13 ); those conducted are limited to monitoring its primary biodegradation (i.e., the disappear ance of the surfactant) or to its mineralization in estuaries (). The primary degradation and mineralization kinetics for LAS under aerobic conditions have previously been characterized in continental ( , ), estuarine ( , ), and marine waters ( − ). Some of the mathematical equations that have been proposed to describe the kinetics of the process are based on curve fitting of the experimental substrate consumption or CO 2 production during biodegradation ().…”

Comprehensive review of several surfactants in marine environments: Fate and ecotoxicity

“…There is considerable variability among studies in all 4 surfactants (shown by large data ranges), with many studies revealing marine surfactant biodegradation to be a long process. It is argued that such data variability may be explained by natural variation (between different environments) and microbial variation by different pretreatment methods (e.g., acclimation history of associated microbial communities to surfactants ), humic substance association, cometabolic transformation, or nutrient‐level variation . Primary biodegradability of LAS homologs has been shown to increase with alkyl chain length , although Larson et al found that LAS mineralization was relatively unaffected by such structural differences.…”

Biodegradation of Linear Alkylbenzene Sulfonate (LAS) by Immobilized <i>Pseudomonas</i> sp.

“…The flow rate was set to 1ml per minute. Data acquisition and processing were performed by using LC solution system (Shimadzu) [15].…”