Alternative inocula as activated sludge surrogate culture for a toxicity test

Abstract

The use of activated sludge to assess the potential toxicity and environmental impact of chemicals and wastewaters suffers from several drawbacks related to the heterogeneity, absence of standardization, and health risk associated with this mixed-sewage population. To search for reliable testing inoculum alternatives, the performance of two commercial inocula (BI-CHEM and BIOLEN M112), a garden-soil inoculum and a pure culture of Pseudomonas sp., was compared with an activated sludge inoculum (AS) in the inhibition respiration test ISO 8192-1986 (E). The respiration rates of microbial inocula were assayed for the reference compound 3,5-dichlorophenol. The acute toxicity values (IC(50)) ranged from 6.7 mg/L (Pseudomonas sp.) to 22.7 mg/L (garden soil), overlapping the expected values for activated sludge microorganisms despite the bacterial diversity. The assayed microbial inocula also showed higher reproducibility than AS and an overall similarity of catabolic profiles obtained with Biolog EcoPlates was observed between AS and some mixed inocula. These results point to the potential ability of such inocula as surrogate cultures in relevant activated sludge-based bioassays. New, well-defined, standardized, and safe tools will then be available for monitoring the ecological impact of hazardous substances and effluents, thus providing environmental protection.

Assessing Microbial Communities for a Metabolic Profile Similar to Activated Sludge

“…The use of synthetic medium to grow each of these three consortia was the best methodology, because it enhanced the microbial metabolic responses for substrate use—higher net areas and higher number of substrates used (i.e., increased the metabolic potential). These three model communities, with CLPPs similar to activated sludge CLPPs, have already been tested as a biological reference material in toxicity and biodegradability tests, in which their potential to be used as alternative inocula to activated sludge was demonstrated ( Paixão et al, 2000 , 2006 ; Paixão, Santos, Baeta‐Hall, Tenreiro, and Anselmo, 2003 ; Paixão, Santos, Tenreiro, and Anselmo, 2003 ).…”

“…A quantitative analysis ( Paixão, Santos, Baeta‐Hall, Tenreiro, and Anselmo, 2003 ) was performed by plotting the optical density ratio (OD Ti /OD T0 ) versus time for the 32 wells of EcoPlates, the 96 wells of GN plates, and the 96 wells of GP plates. Each substrate curve was blanked (control A1 curve subtracted), and then the curve‐integration approach was used ( Guckert et al, 1996 ; Hackett and Griffiths, 1997 ).…”

Evaluation and Modification of the OECD 301F Respirometry Biodegradation Test Method with Regard to Test Substance Concentration and Inoculum

“…As the alternative inoculum displayed little endogenous respiration, it is considered that the manner in which this inoculum was isolated from activated sewage and subsequently grown on nutrient rich medium contributed to the observed low level of endogenous respiration, rather than the actual microbial composition of the alternative inoculum. Paixão et al (2000Paixão et al ( , 2003 and Tabka et al (1993) used commercial blends of microorganisms as inocula for biodegradation tests, as they argue that sewage will vary in microbial composition and biodegradative specificity depending on where and when it is sampled. However, inoculum standardisation is criticised by Pagga (1997) and Forney et al (2001), as they suggest that a truly mixed inoculum is required to provide as high a biodegradation potential as possible for all chemicals.…”

Molecular assessment of microbiota structure and dynamics along mixed olive oil and winery wastewaters biotreatment

“…The results obtained were quantitatively (number of positives) and qualitatively (area under the curve of substrate degradation) analyzed, as described by Paixão et al (2003) and Garland and Mills (1991). The first allows the definition of the amount of substrate that must be degraded being considered as a positive result.…”

“…Due the diversity of organic compounds present in these effluents, it was expected that the corresponding microbial communities have the ability to use some of those compounds. An approach to differentiating the microbiota by its catabolic potential is the community level metabolic profile (CLPP) analysis that allows the characterization of the functional potential of the selected microbiota based on its ability to oxidize several carbon sources (Choi and Dobbs 1999;Garland and Mills 1991;Paixão et al 2003).…”