Elsevier

Water Research

Volume 47, Issue 4, 15 March 2013, Pages 1585-1595
Water Research

Microbial kinetic model for the degradation of poorly soluble organic materials

https://doi.org/10.1016/j.watres.2012.12.013Get rights and content

Abstract

A novel mechanistic model is presented that describes the aerobic biodegradation kinetics of soybean biodiesel and petroleum diesel in batch experiments. The model was built on the assumptions that biodegradation takes place in the aqueous phase according to Monod kinetics, and that the substrate dissolution kinetics at the oil/water interface is intrinsically fast compared to biodegradation kinetics. Further, due to the very low aqueous solubility of these compounds, the change in the substrate aqueous-phase concentration over time was assumed to approaches zero, and that substrate aqueous concentration remains close to the saturation level while the non-aqueous phase liquid (NAPL) is still significant. No former knowledge of the saturation substrate concentration (Ssat) and the Monod half-saturation constant (Ks) was required, as the term Ssat/(Ks + Ssat) in the Monod equation remained constant during this phase. The n-alkanes C10–C24 of petroleum diesel were all utilized at a relatively constant actual specific utilization rate of 0.01–0.02 mg-alkane/mg-biomass-hr, while the fatty acid methyl esters (FAMEs) of biodiesel were utilized at actual specific rates significantly higher with increasing carbon chain length and lower with increasing number of double bonds. The results were found to be in agreement with kinetic, genetic, and metabolic evidence reported in the literature pertaining to microbial decay rates, uptake mechanisms, and the metabolic pathway by which these compounds are assimilated into microorganisms. The presented model can be applied, without major modifications, to estimate meaningful kinetic parameters from batch experiments, as well as near source zone field application. We suggest the estimated actual microbial specific utilization rate (kC) of such materials to be a better measure of the degradation rate when compared to the maximum specific utilization rate (k), which might be orders of magnitude higher than kC and might never be observed in reality.

Highlights

► We derived a novel kinetic model for biodegradation of poorly soluble materials. ► The model fits well the observed data of degradation of petrodiesel and biodiesel. ► The results were found to be supported by kinetic, genetic, and metabolic evidence. ► The model provides a robust tool in analyzing the biodegradation of such materials.

Introduction

Poorly soluble materials such as lipids and petroleum products have always presented a serious threat to natural habitats. It is estimated that lipids make up to 23–52% of the typical waste coming into wastewater treatment plants (Chipasa and Mdrzycka, 2006), while petroleum hydrocarbons are considered one of the major surface and subsurface water contaminants (Kvenvolden and Cooper, 2003). Although many studies investigating the microbial utilization of such materials have been reported in the literature, the majority of these studies usually report their findings using first order decay rates with respect to the total substrate. Theoretical examinations of such mechanisms have always remained an active area of research (Aiba et al., 1969; Beolchini et al., 2010; Blanch and Einsele, 1973; Chakravarty et al., 1975; Erickson et al., 1969; Miura et al., 1977; Moo-Young and Shimizu, 1971; Ramaswami and Luthy, 1997; Yoshida et al., 1971).

Owing to their poor solubility in water (10−4 to 10−10 g/L for C10 to C24 n-alkanes) (Ferguson et al., 2009; McAuliffe, 1969), the biological assimilation of poorly soluble materials is often modeled to occur at the oil/water interface by direct contact between microorganisms and oil droplets. Johnson and Aiba et al. independently concluded that microorganisms take up liquid hydrocarbons by direct contact with the oil surface and that dissolved hydrocarbons made negligible contributions to overall growth rates, mainly based on empirical calculations of liquid solubilities and diffusivities of longer n-alkanes (Aiba et al., 1969; Johnson, 1964). Erickson and Humphery developed multiple kinetic models that describe the growth of microorganisms on the surface of liquid hydrocarbons and treated the contribution of dissolved substrate to the microbial growth as a secondary mechanism (Erickson and Humphrey, 1969). However, they did not provide any experimental verification for their modeling approach.

In the surface attachment modeling approach, the microbial growth limiting factor is assumed to be the available interfacial surface area of the oil droplets (Erickson and Humphrey, 1969; Moo-Young and Shimizu, 1971). Although microorganisms having the ability to attach to oil's surface have been documented in the literature (Bouchez-Nailtali et al., 2001; Rosenberg, 2006), a larger number of cells often remains unattached to the oil droplets even when the available surface area of the oil is relatively large compared to the population of cells (Chakravarty et al., 1975; Miller and Johnson, 1966). In addition, mechanisms of substrate transport from the bulk organic phase directly into the biomass without passing through the aqueous phase are not completely understood (Chakravarty et al., 1975). To test the microbial surface attachment hypothesis, Yoshida et al. compared the growth rates of Candida tropicalis on liquid and vapor n-hexadecane in two different fermentors (Yoshida et al., 1971). The specific growth rate of the microorganisms on the vapor hexadecane was found to be the same as that on liquid hexadecane. They concluded that microbial hydrocarbon uptake by direct contact with the liquid hydrocarbon is negligible. Blanch and Einsele (Blanch and Einsele, 1973) also investigated the growth of C. tropicalis on n-hexadecane and found that the growth rate in the exponential growth phase was independent of mixing speed. They concluded that the surface attachment mechanism was not responsible for growth.

In contrast to the surface attachment modeling approach, the biodegradation of poorly soluble materials has also been modeled to occur inside the aqueous phase by coupling the Monod equation (Monod, 1949) with equilibrium substrate partitioning (Ostendorf et al., 2007) or linear driving force dissolution (Seagren et al., 1994) models, in which the substrate has to dissolve into the aqueous phase prior to microbial utilization. These models often yield complex governing equations that are either solved numerically (Chu et al., 2003), or by finite (Ostendorf et al., 2007) or infinite (Chu et al., 2007) series approximations, or further simplified by imposing constitutive assumptions such as steady state biomass growth or by assuming that the substrate concentration is significantly small compared to the Monod half-saturation constant (i.e. Sw << Ks) (Seagren et al., 1994).

The choice of an appropriate degradation kinetics model seems to be influenced by the type of degrading organism as much as the type of material being degraded. However, when the degrading organisms are unknown, which is the case in most environmental applications, we have assumed that microbial growth occurs on the organic matter that is dissolved in the aqueous phase. The purpose of this paper was to develop a novel mechanistic but fairly simple microbial kinetic model for the degradation of poorly soluble organic materials. The objective was to obtain a more user-friendly analytical tool that is founded on accepted phenomenological principles, as opposed to the more tedious computationally intensive approaches, or statistical “black box” methods. The model was built on the accepted assumptions that the substrate dissolution at the oil/water interface is intrinsically fast compared to the biological reaction (Mihelcic et al., 1993; Rivett and Feenstra, 2004; Seagren et al., 1999), and that the substrate has to dissolve into the aqueous phase prior to biological utilization inside the aqueous phase according to the infamous Monod growth kinetics (Monod, 1949). The derived model was able to adequately explain 90–97% of the aerobic biodegradation kinetics of the fatty acid methyl esters (FAMEs) of soybean biodiesel, and 80–94% of the biodegradation kinetics of the n-alkanes of petroleum diesel in batch experiments by acclimated cultures.

Section snippets

Chemicals

Low-sulfur petroleum diesel (B0) was purchased from a BP diesel station (Cincinnati, Ohio) with an n-alkanes mole fraction of 0.165. Unblended soybean-methyl ester biodiesel (B100) was purchased from Peter Cramer North America (Cincinnati, Ohio) with FAMEs mole fractions of 0.145 C16:0, 0.055 C18:0, 0.206 C18:1, 0.518 C18:2, and 0.0759 C18:3. Palmitic acid methyl ester (99%) (C16:0-ME), palmitoleic acid methyl ester (99%) (C16:1-ME), stearic acid methyl ester (99%) (C18:0-ME), oleic acid methyl

Results and discussion

Negligible abiotic disappearance of the n-alkanes was observed in the abiotic controls (i.e., kab = 0). For the FAMEs, the term (kab·Ssat) ranged from 0.055 mg/L-h for C18:0-ME to 0.641 mg/L-h for C18:2-ME, correlating very well with the aqueous solubilities of these FAMEs approximated by Raoult's law using pure solubilities reported by Krop et al. (1997). This supports the assumption made earlier that the abiotic transformation of the FAMEs might have occurred or even further enhanced inside

Conclusion

A novel and simple mechanistic equation for the kinetics of microbial degradation of poorly soluble organics was developed and tested in this paper. The modeling approach was based on the assumptions that substrate utilization takes place in the aqueous phase according to Monod kinetics, and negligible weight was given to the oil-attached microbial growth mechanism. This assumption was adopted because the capability of microorganisms to attach on oily surfaces is often undetermined in

Acknowledgment

Funding of this research was made possible through the U.S. Environmental Protection Agency (U.S. EPA) Oil Spill Research Program managed by the Land Remediation and Pollution Control Division of the National Risk Management Research Laboratory, Cincinnati, OH, under Contract No. EP-C-11-006, Work Assignment 1-19.

References (54)

  • E.A. Seagren et al.

    A critical evaluation of the local-equilibrium assumption in modeling NAPL-pool dissolution

    Journal of Contaminant Hydrology

    (1999)
  • K. Yamada-Onodera et al.

    Degradation of long-chain alkanes by a polyethylene-degrading fungus, Penicillium simplicissimum YK

    Enzyme and Microbial Technology

    (2002)
  • S. Aiba et al.

    Cultivation of yeast cells by using n-alkanes as sole carbon source. 2. An approach to mechanism of microbial uptake of n-alkanes

    Journal of Fermentation Technology

    (1969)
  • H.W. Blanch et al.

    The kinetics of yeast growth on pure hydrocarbons

    Biotechnology and Bioengineering

    (1973)
  • M. Bouchez-Naïtali et al.

    Evidence for interfacial uptake in hexadecane degradation by Rhodococcus equi: the importance of cell flocculation

    Microbiology

    (2001)
  • M.H. Brodnitz

    Autoxidation of saturated fatty acids. A review

    Journal of Agricultural and Food Chemistry

    (1968)
  • D.K. Button et al.

    Viability and isolation of marine bacteria by dilution culture: theory, procedures, and initial results

    Applied and Environmental Microbiology

    (1993)
  • M. Chakravarty et al.

    A kinetic model for microbial growth on solid hydrocarbons

    Biotechnology and Bioengineering

    (1972)
  • M. Chakravarty et al.

    A kinetic model for microbial growth on liquid hydrocarbons

    Biotechnology and Bioengineering

    (1975)
  • K.B. Chipasa et al.

    Behavior of lipids in biological wastewater treatment processes

    Journal of Industrial Microbiology and Biotechnology

    (2006)
  • H. de Jonge et al.

    Relation between bioavailability and fuel oil hydrocarbon composition in contaminated soils

    Environmental Science & Technology

    (1997)
  • L.E. Erickson et al.

    Growth models of cultures with two liquid phases. II. Pure substrate in dispersed phase

    Biotechnology and Bioengineering

    (1969)
  • L.E. Erickson et al.

    Growth models of cultures with two liquid phases. I. Substrate dissolved in dispersed phase

    Biotechnology and Bioengineering

    (1969)
  • H.L. Fang et al.

    Spectroscopic study of biodiesel degradation pathways

    SAE Technical Papers

    (2006)
  • A.L. Ferguson et al.

    Solubility and molecular conformations of n-alkane chains in water

    The Journal of Physical Chemistry B

    (2009)
  • P. Gikas et al.

    Use of ATP to characterize biomass viability in freely suspended and immobilized cell bioreactors

    Biotechnology and Bioengineering

    (1993)
  • E. Holder et al.

    Crude Oil Component Biodegradation Kinetics by Marine and Freshwater Consortia

    (1999)
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