Biodegradation Curves Research Articles

Biodegradation kinetics of oil palm empty fruit bunches by white rot fungi

The biodegradation of lignin, cellulose and hemicellulose from oil palm empty fruit bunches by white rot fungi Phanerochaete chrysosporium and Pleurotus ostreatus was investigated. The results showed higher mass loss and polysaccharide degradation when the biological treatment was carried out with P. chrysosporium. Biodegradation curves were modelled by a Weibull kinetic model and the kinetic parameters were obtained for each one of the components. Even though the lignin degradation rates were similar for both fungi, the biodegradation of this component reached 50% with P. ostreatus, a higher value than the 41% reached with P. chrysosporium after harvesting for four weeks. Higher polysacharides biodegradation rates were observed for P. chrysosporium compared to P. ostreatus. Consequently, the P. ostreatus pretreatment can be considered adequate for the delignification of palm residues without considerably affecting the cellulose fraction, which is important for the production of fermentable sugars.

Study on biodegradability of terephthalic acid in polyester fabric alkali-peeling process wastewater

Terephthalic acid (TA) and ethylene glycol (EG) are the main pollutants in polyester fabric alkali-peeling process wastewater (PAP-wastewater). The biodegradability of TA is crucial to the deep treatment of PAP-wastewater. Batch and continuous experiments were adopted to study the biodegradation of TA in synthetic wastewater. In anoxic batch experiments TA began to degrade gradually after EG was depleted completely. However, in aerobic batch experiments the biodegradation curves of TA in the presence of EG were almost identical to those of TA in the absence of EG. The combined process of anoxic hydrolysis-acidification bioreactor (HABR) and aerobic hybrid membrane bioreactor (HMBR) was employed to treat synthetic PAP-wastewater in continuous experiments. When TA was fed as sole substrate, about 6.1% was removed in the anoxic HABR and 92.1% was biodegraded in the aerobic HMBR. When TA and EG were fed as substrate, only 1.9% of TA was biodegraded in the anoxic HABR and 96.6% of TA was removed in the aerobic HMBR. By contrast, most EG was removed in the anoxic HABR. The experimental results revealed that the combined process of anoxic HABR and aerobic HMBR was an attractive alternative for the treatment of PAP-wastewater and other similar wastewater.

Initiating Biodegradation of Polyvinylpyrrolidone in an Aqueous Aerobic Environment: Technical Note / Zainicjowanie Biodegradacji Poliwinylopirolidonu W Środowisku Wodno-Tlenowym: Notatki Techniczne

Abstract A synthetic polymer, polyvinylpyrrolidone (PVP - E 1201) primarily finds applications in the pharmaceutical and food industries due to its resistance and zero toxicity to organisms. After ingestion, the substance passes through the organism unchanged. Consequently, it enters the systems of municipal wastewater treatment plants (WWTP) without decomposing biologically during the waste treatment process, nor does it attach (through sorption) to particles of activated sludge to any significant extent, therefore, it passes through the system of a WWTP, which may cause the substance to accumulate in the natural environment. For this reason the paper investigates the potential to initiate aerobic biodegradation of PVP in the presence of activated sludge from a municipal wastewater treatment plant. The following agents were selected as the initiators of the biodegradation process - co-substrates: acrylamide, N-acethylphenylalanine and 1-methyl-2-pyrrolidone, a substance with a similar structure to PVP monomer. The biodegradability of PVP in the presence of co-substrates was evaluated on the basis of biological oxygen demand (BOD) as determined via a MicroOxymax O2/CO2/CH4 respirometer. The total substrate concentration in the suspension equaled 400 mg·dm-3, with the ratio between PVP and the cosubstrate being 1:1, while the concentration of the dry activated sludge was 500 mg·dm-3. Even though there was no occurrence of a significant increase in the biodegradation of PVP alone in the presence of a co-substrate, acrylamide appeared to be the most effective type of co-substrate. Nevertheless, a recorded decrease in the slope of biodegradation curves over time may indicate that a process of primary decomposition was underway, which involves the production of metabolites that inhibit activated sludge microorganisms. The resulting products are not identified at this stage of experimentation.

Persistency assessment and aerobic biodegradation of selected cyclic sesquiterpenes present in essential oils

Sesquiterpenes are ubiquitous in essential oils but an assessment of their environmental behavior is still required for their use as components of natural fragrance ingredients and oral care flavors. Persistency plays a key role in hazard and risk assessment, but the current knowledge on the biodegradation of sesquiterpenes in the aquatic environment is limited. This could have important consequences for the persistent, bioaccumulative and toxic (PBT) assessment of essential oils because most of the sesquiterpene components have a log K(OW) of >4.5 and are identified as potentially bioaccumulating according to REACH screening criteria. In the present study, a persistency screening assessment was conducted on 11 cyclic sesquiterpenes selected from 10 different families of sesquiterpenes characterized by their carbon skeleton. Current biodegradation prediction models (BioWin™, BioHCwin, and Catalogic) were found to be of limited use because most of the sesquiterpenes studied were outside the structural domain of the models. Aerobic biodegradation was measured in a standard or prolonged Organisation for Economic Co-operation and Development (OECD) 301F Manometric Respirometry test for ready biodegradability. α-Bisabolol, α-humulene, β-caryophyllene, α-cedrene, cedrol, longifolene, and δ-cadinene exceeded the pass level of 60% degradation and can be regarded as not persistent. Alpha-gurjunene, himachalenes (α, β, γ), and (-)-thujopsene almost achieved the pass level reaching between 51% and 56% ultimate biodegradation. Although germacrene D only achieved 24% ultimate biodegradation, specific analysis at the end of the test did indicate complete primary degradation. Given that the shape of the biodegradation curves indicates poor bioavailability and ready biodegradability tests are very stringent, it is expected that all the sesquiterpenes tested in the present study would be degraded under environmental conditions.

BIODEGRADATION OF ENDOCRINE DISRUPTERS: CASE OF 17β‐ESTRADIOL AND BISPHENOL A

The biodegradation of 17 β‐estradiol (E2) and bisphenol A (BPA) was compared to that of a reference pollutant, sodium benzoate (SB), known for its high biodegradability. The biodegradation was measured using the Sturm test (ISO 9439 modified Sturm test). The susceptibility of the target pollutants to be degraded by microorganisms of activated sludge from a wastewater treatment plant (WWTP) was evaluated by the production of carbon dioxide (CO2). Sorption experiments onto inactivated sludge were carried out to assess the contribution of sorption in E2 and BPA removal during biological treatment in a WWTP. E2 was more adsorbed than BPA onto inactivated sludge, probably making it less accessible to assimilation by microorganisms. In fact, E2 was less biodegradable than BPA with 66 % and 74 % of theoretical CO2 formation (ThCO2) in 28 days, respectively. However, E2 showed faster biodegradation than BPA due to the shorter adaptation time of the microorganisms to start the assimilation. Final concentrations were measured and revealed that, under Sturm test conditions, E2 was totally removed from the aqueous phase while some traces of BPA were detected. This result could be explained by the lower adsorbability of BPA observed in adsorption experiments onto inactivated sludge. To investigate competition in a bi‐component solution, Sturm tests were carried out with BPA/SB and E2/SB. Moreover, the biodegradation curves obtained did not indicate a toxicity of the target compounds towards microorganisms, which rapidly degraded SB. In the case of BPA/SB, an inflection in the curve confirmed the adaptation time of 4–5 days for BPA to be degraded.

Method of Producing Biodegradable Reference Material and its Biodegradability Based on International Standard Evaluation Method (ISO 14855-2)

Returnable cups made of poly(lactic acid) (PLA) are employed as an example of products made of biodegradable plastics. Two kinds of PLA samples plates and powders with different shapes were prepared from PLA cups. The plates were cut from a cup using nippers. Powders were prepared using a rotation mechanical mixer for 45 min. PLA powders were separated by sieves with 60 meshes (250 μm) into a size ranging from 0 to 250 μm. An average diameter of powders separated by a sieve is 169 μm. Biodegradation tests of PLA plates, PLA powders and cellulose powders in controlled compost at 58 °C were performed using a Microbial Oxidative Degradation Analyzer (MODA) instrument according to ISO 14855-2. PLA powders showed almost the same biodegradation curve as that of cellulose powders. PLA plates biodegraded at a slower rate than PLA powders.

Enhanced Degradation of n-Hexadecane in Diesel Fuel Contaminated Soil by the Addition of Fermented Whey

The objective of this work has been to investigate the possibility of using fermented whey as an organic growth supplement in order to enhance the aerobic degradation of n-hexadecane in soil. Fermented whey was added at different dosages to nutrient amended soil microcosms contaminated with 5000 mg diesel fuel kg−1 dry weight (dw). The target substance was 14C-labeled n-hexadecane, and the biodegradation was monitored by analysis of evolved 14CO2. Biodegradation curves were fitted to a three-half-order kinetics model. Enhanced biodegradation was observed in sand at 7 and 22°C and in loamy sand at 22°C but the effect was most pronounced in the sand soil at 22°C. The addition of 6 or 60 ml fermented whey kg− 1 soil dw increased the degree of n-hexadecane biodegradation at the end of the experiment, 167 days, from 49% in the untreated sand to 60 or 67%, respectively. This increase in biodegradation was characterized by an increase in the amount of substrate biodegradation by first-order kinetics despite a decrease in the first order rate constant, k1. The highest concentration of fermented whey, 60 ml kg−1, gave rise to substrate competition, diauxie, which resulted in an extended lag phase.

Modelagem empírica do processo de biodegradação de efluentes protéicos por enzimas de Carica papaya sp.

O objetivo deste trabalho foi modelar empiricamente a biodegradação de efluentes protéicos por enzimas papaínas do látex de Carica papaya sp. num biorreator agitado, para facilitar a otimização do processo por metodologia de análise de superfície de resposta (RSM) e aplicar em tratamento de efluentes provenientes de indústrias de processamento de carne. As análises das curvas de biodegradação mostraram que o tempo de residência para os biorreatores está entre 28 e 30 h. O modelo empírico que mais se ajustou aos dados de biodegradação sob influência dos fatores (pH e temperatura) foi o de um hiperplano e a região de operação otimizada para a degradação de proteínas pelas papaínas foi aquela que apresentou os maiores valores de temperatura e menores valores de pH.

Metodyka oceny biodegradowalnosci polimerow w badaniu ich przydatnosci do odzysku organicznego w wyniku kompostowania

The results of experiments aimed at elaborating the procedure of preliminary assessment of biodegradability were presented. The assessment was needed for estimation of usability for composting of packaging materials made of biodegradable polymers. Pilot test stand for measuring of polymer biodegradation during composting was designed and installed (Fig. 1). Test of selected polymer biodegradation, with microcrystalline cellulose as reference material, was carried out in the stand (Table 1). Comparative curves of CO2 formation (Fig. 3) and biodegradation curves (Fig. 4) were prepared. The results of biodegradation degree calculation either on the basis of amount of evolved CO2 measurement or standardized measurement of organic substance weight loss were compared (Table 2). Technical limitations making impossible the proper assessment of biodegradation course in the stand used were discussed and the solutions allowing to eliminate the shortcomings observed were pointed out.

Biodegradation of chemicals in a standardized test and in environmental conditions

The estimation of biodegradation rates is an important source of uncertainty in chemical risk assessment. The existing OECD tests for ready biodegradability have been developed to devise screening methods to determine whether a chemical is potentially easily biodegradable, rather than to predict the actual rate, of biodegradation in the environment. However, risk assessment needs degradation rates. In practice these rates are often estimated (default values) from ready biodegradability tests. These tests have many compromising arbitrary features compared to the situation in the real environment. One important difference is the concentration of the chemical. In wastewater treatment or in the environment many chemicals are present at ng l −1 to μg l −1 levels whereas in the tests the concentrations exceed 10–400 mg carbon per litre. These different concentrations of the chemical will lead to different growth kinetics and hence different biodegradation rates. At high concentrations the chemical, if it is degradable, can serve as a primary substrate and competent microorganisms will grow exponentially, resulting in a sigmoid biodegradation curve. At low environmental concentrations the chemical does not serve as a primary substrate, and therefore does not support significant growth of the degraders, and the substrate has a linear biodegradation rate. In this study the biodegradation rates of two reference chemicals, aniline and 4-chloroaniline, were compared in a standard method and in more realistic conditions at low concentrations, using 14C-labelled substances and different sources of inocula. Biomass evolution during the tests was monitored by adenosine triphosphate measurement and also on the basis of the residual 14C-activity in the particulate matter. The results partly support the thesis that low concentrations lead to different biodegradation kinetics compared to the concentrations used in the standard tests. Furthermore the biodegradation rates of the chemicals studied, particularly of 4-chloroaniline, in Finnish natural waters appeared to be lower than those reported in some other countries.

Modelling Easily Biodegradability of Materials in Liquid Medium-Relationship Between Structure and Biodegradability

In the present project, twenty materials (e.g., polyhydroxybutyrate-hydroxyvalerate, polycaprolactone, cellulose acetate, polyacticacid, polyethylene), representing varied biodegradability levels were studied. An aerobic respirometric test, based on the CEN Draft, was setup. The biodegradability of each plastic film was evaluated by measuring the percentage of carbon converted into CO2 during 35 days. The values of the CO2 production were plotted versus days as a cumulative function. In order to reduce its number of points, the cumulative curve was modeled using a sigmoid function (Hill sigmoid). This model was compared to one found in the literature. A χ i 2 test showed that the biodegradation curve was more accurately fitted with the model than the previous one. Three kinetic parameters were determined by this “Hill model”: one represents the maximal percentage of carbon converted into CO2, the second the “half-life time” in days of the degrading part of the material and the third one the curve radius. In addition, the following analyses were carried out on each sample: elemental analysis, thickness, hydrophobicity and surface free energy measurements. In order to compress the information and to keep only relevant pieces, these parameters were submitted to a Principal Component Analysis. PCA found linear combinations of variables that describe major trends in the data. The two principal components which separate groups of materials were closely related to a chemical and a physical axis respectively. Materials showing a high biodegradability were related to high oxygen (and nitrogen) contents and low hydrophobicity: Material thickness did not influence the likeliness to biodegradability described by the maximum biodegradation rate. Finally, this study established the correlation between the biodegradation and the structure of biopolymers.

Evaluation of the Biodegradation of Starch and Cellulose Under Controlled Composting Conditions

In order to verify the response of the controlled composting test method (i.e., the ISO/DIS 14855:1997, the ASTM D 5338-92, or the CEN counterpart) to starch at different concentrations, the maximum amount prescribed by the test method (100 g) and lower amounts (60 and 30 g), as if starch were a coingredient in a blend, were tested. After 44 days of incubation (at a constant temperature of 58°C) the biodegradation curves were in a plateau phase, displaying the following final values (referred to a nominal starch initial amount of 100 g): starch 100 g, 97.5%; starch 60 g, 63.7%; and starch 30 g, 32.5%. The data show a CO2 evolution roughly equal, in each case, to the theoretical maximum, indicating a complete starch mineralization. We cannot discern whether the deviations found at lower concentrations are caused by a priming effect. In any case, the extent of the deviations is not high and is acceptable in biodegradation studies. The average biodegradation of cellulose, obtained gathering four independent experiments with 11 biodegradation curves, turned out to be 96.8 ± 6.7% (SD) after 47 ± 1 days. The data indicate that the controlled composting is a reliable test method also for starch and cellulose and, consequently, for starch-based and cellulose-based materials.

Lack of Capsular Exopolymer Effects on the Biodegradation of Organic Compounds by Pseudomonas sp. Strains JS1 and JS150

Due to the increasing interest in the effects of exopolymers on microbial activities, two Pseudomonas sp. strains, JS1 (possesses capsular exopolymer) and JS150 (unencapsulated), were compared for their ability to degrade a variety of organic compounds under a number of different conditions. Degradation kinetics for citrate, salicylate, phenol, toluene, and 2,4,6-trinitrotoluene were identical for both strains in liquid media, regardless of cell density. JS1 and JS150 grew on citrate at the same rate in sand, sterile surface soil, and sterile subsurface sediments. The biodegradation curves for toluene by cells pregrown on citrate in any of the above matrices were indistinguishable. Twofold differences in water content and carbon-to-nitrogen ratios of 0.032 or 320 did not result in any apparent differences in phenol degradation by either encapsulated or unencapsulated cells in sand. These results indicate that generalizations about the effects of exopolymers on microbial processes may not be possible without further research.

A respirometer with improved sensitivity for ready biodegradation testing

In this paper we describe a respirometry system with improved sensitivity, that was used to test materials at concentrations down to 3 mg C/l. Data obtained with this system, operating under the conditions of the OECD ready biodegradability tests 301B, C, D and F, is presented and compared with CO 2-production data obtained under 301B conditions in the Sealed Vessel Test. For simple materials, the shape of the curves, not easily seen with CO 2 production or DOC removal data, is clearly biphasic with a sigmoidal first part — suggesting growth of the inoculum on the test materials. For a selection of rapidly and readily biodegradable materials, the removal of soluble carbon was complete at the end of the first, sigmoidal part of the biodegradation curve; It is speculated that the remainder of the curve probably represents the mineralisation of part of the biomass. The respirometer generated many hundred data points per degradation curve and Monod or exponential growth models were fitted and growth parameters were derived. Growth rates under ready test conditions were derived for six materials as follows: aniline μ = 0.31 h −1, ethanolamine μ = 0.13 h −1, 1,6-hexanediol μ = 0.05 h −1, pentaerythritol μ = 0.04 h −1, C12.8EO μ = 0.13 h −1 and commercial LAS μ = 0.05 h −1.

Substrate availability in phenanthrene biodegradation: Transfer mechanism and influence on metabolism

The mechanism of phenanthrene transfer to the bacteria during biodegradation by a Pseudomonas strain was investigated using a sensitive respirometric technique (Sapromat equipment) allowing the quasi-continuous acquisition of data on oxygen consumption. Several systems of phenanthrene supply, crystalline solid and solutions in non-water-miscible solvents (silicone oil and 2,2,4,4,6,8,8-heptamethylnonane) were studied. In all cases, analysis of the kinetics of oxygen consumption demonstrated an initial phase of exponential growth with the same specific growth rate. In order to analyze the second phase of growth and phenanthrene degradation, a study of the kinetics of phenanthrene transfer to the aqueous phase was conducted by direct experimentation, with the crystal and silicone oil systems, in abiotic conditions. The data allowed the validation of a model based on phase-transfer laws, describing the variations, with substrate concentrations, of rates of phenanthrene transfer to the aqueous phase. Analysis of the biodegradation curves then showed that exponential growth ended in all cases when the rates of phenanthrene consumption reached the maximal transfer rates. Thereafter, the biodegradation rates closely obeyed, for all systems, the transfer rate values given by the model. These results unambiguously demonstrated that, in the present case, phenanthrene biodegradation required prior transfer to the aqueous phase. With the silicone oil system, which allowed high transfer and biodegradation rates, phenanthrene was directed towards higher metabolite production and lower mineralization, as shown by oxygen consumption and carbon balance determinations.

Influence of the Size and Source of the Inoculum on Biodegradation Curves in Closed-Bottle Tests

Test variables influencing the results of the closed-bottle test include size and source of the inoculum. The inoculum originates from activated sludge plants maintained at various sludge retention times. The lag period prior to biodegradation, which is influenced primarily by acclimation, decreased with increasing numbers of competent microorganisms. The rate of biodegradation in the closed-bottle test is influenced by the sludge retention time by which the inocula are maintained. Acclimated sludges maintained at low sludge retention times used as inocula gave biodegradation curves with steep slopes, indicating degradation at high rates. Therefore, unacclimated ready biodegradability tests enable only conservative assessments of the biodegradation potential of wastewater purification plants. The results reported here demonstrate that other tests should be used in risk assessment to estimate the full biodegradation potential in wastewater treatment plants.

A simple method for quantifying activity and survival of microorganisms involved in bioremediation processes.

We have developed a substrate-induced growth response (SIGR) method for quantifying activity and population dynamics of microorganisms involved in bioremediation processes in soil and bioreactors. The biomass of organisms that can mineralize a given chemical can be estimated based on the concentration of that chemical needed to induce the growth of the standing population. Estimates of population size are obtained by using nonlinear regression techniques to fit a simple model of microbial population dynamics to biodegradation curves. Using this approach we obtain estimates of values for parameters such as initial population size and growth rate of organisms carrying out biodegradative processes. Our approach was validated by comparing model parameter estimates with independent estimates of the same parameters from the same bioremediation systems. Examples studied include pentachlorophenol degraders introduced into soil and 2,4-dinitrophenol degrading organisms in a bioreactor.

Biodegradability of ethoxylated fatty amines: detoxification through a central fission of these surfactants

Non-ionic surfactants are initially degraded by a central fission of the molecule or by the oxidation of the far end of the polyoxyethylene (EO) chain. Alcohol ethoxylates are metabolized via a central fission, whereas alkylphenol ethoxylates are degraded by a stepwise shortening of the polyoxyethylene moiety. The biodegradation curves of ethoxylated fatty amines suggest a ‘rapid’ mineralization via an oxidation of the alkyl chain. The intermediates formed, viz., secondary ethoxylated amines, are ‘slowly’ biodegraded. This ‘total’ mineralization of the ethoxylated fatty amines was demonstrated in ‘prolonged’ Closed-Bottle tests. Decisive evidence for a central fission of ethoxylated fatty amines was obtained in a pure culture study. An isolated Pseudomonas sp. cleaved the C alkyl-N bond of octadecylbis(2-hydroxyethyl) amine and utilized the alkyl chain as sole carbon and energy source. Biodegradation products of both alcohol ethoxylates and ethoxylated fatty amines, formed through a central fission of the molecule, are non-toxic.

Metabolic pathway for the biodegradation of octadecylbis(2-hydroxyethyl)amine

The biodegradation curve of octadecylbis(2-hydroxyethyl)amine determined in a Closed Bottle test suggested an initial oxidation of the alkyl chain and a subsequent degradation of the diethanolamine formed. Using the sludge from the test as inoculum, a bacterium capable of utilizing octadecylbis(2-hydroxyethyl)amine as sole source of carbon and energy was isolated. This bacterium also utilized various other alkylbis(2-hydroxyethyl)amines and octadecylpolyoxyethylene(5)amide. Respirometric studies and the formation of diethanolamine by a washed cell suspension of the pure culture showed that the bacterium only oxidized the alkyl chain. Furthermore, in cell-free extracts a dehydrogenase activity catalysing the oxidation of octadecylbis(2-hydroxyethyl)amine was detected.

Biologischer Abbau von NTA im Weser- Ästuar / Biodegradation of Nitrilotriacetic Acid (NTA) in Weser Estuarine Water

The biodegradation of nitrilotriacetic acid (NTA) at concentrations of 1, 10, 100 and 1000 ng/ml in German estuarine water was determined. The shapes of the biodegradation curves were unusual and biodegradation occurred in two stages in cases where microbial growth was required for the completion of degradation