Abstract: Cellulose acetate polymer is used to make a variety of consumer products including textiles, plastic films, and cigarette filters. A review of degradation mechanisms, and the possible approaches to diminish the environmental persistence of these materials, will clarify the current and potential degradation rates of these products after disposal. Various studies have been conducted on the biodegradability of cellulose acetate, but no review has been compiled which includes biological, chemical, and photo chemical degradation mechanisms. Cellulose acetate is prepared by acetylating cellulose, the most abundant natural polymer. Cellulose is readily biodegraded by organisms that utilize cellulase enzymes, but due to the additional acetyl groups cellulose acetate requires the presence of esterases for the first step in biodegradation. Once partial deacetylation has been accomplished either by enzymes, or by partial chemical hydrolysis, the polymer’s cellulose backbone is readily biodegraded. Cellulose acetate is photo chemically degraded by UV wavelengths shorter than 280 nm, but has limited photo degradability in sunlight due to the lack of chromophores for absorbing ultraviolet light. Photo degradability can be significantly enhanced by the addition of titanium dioxide, which is used as a whitening agent in many consumer products. Photo degradation with TiO2 causes surface pitting, thus increasing a material’s surface area which enhances biodegradation. The combination of both photo and biodegradation allows a synergy that enhances the overall degradation rate. The physical design of a consumer product can also facilitate enhanced degradation rate, since rates are highly influenced by the exposure to environmental conditions. The patent literature contains an abundance of ideas for designing consumer products that are less persistent in the outdoors environment, and this review will include insights into enhanced degradability designs.

Abstract: In this study we compare the biodegradation of both single-walled (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) using two different oxidative conditions. In particular, we demonstrate that oxidized multi-walled carbon nanotubes are highly degraded, although not to completeness when treated with horseradish peroxidase (HRP) in the presence of hydrogen peroxide.

Abstract: This work presents the last phase of long-term experimental studies on the biodegradation in soil behaviour of polymers destined for agricultural applications. The paper focuses on comparative studies between the biodegradation in soil behaviour of two important biodegradable polymers based on renewable resources: poly(lactic acid) (PLA) versus polyhydroxyalkanoates (PHA). Full-scale experiments were carried out during the period June 2008–January 2009. Different methods of exposure were applied in the case of polyhydroxyalkanoates, simulating the agricultural biodegradable mulching films use and their fate in soil after the end of their useful lifetime. The field results were compared with the results of biodegradation under controlled laboratory conditions simulating biodegradation in soil, using soil from the experimental field. Further, the field results were compared against the results of biodegradation under farm composting conditions.

Abstract: Fungi, isolated from sea water, were subjected to growth in a medium containing low density polyethylene (LDPE) as the sole carbon source with and without yeast extract. Increasing fresh weight of the fungi in the medium supplemented with LDPE after regular time intervals gave the evidence that the fungi were utilizing LDPE as the carbon source. Further confirmation of LDPE utilization was carried out by the Sturm test where the degradation was attributed to the amount of carbon dioxide evolved during the growth period. The two fungi that showed good growth in medium supplemented with LDPE proved to degrade LDPE with higher efficiency in earlier reported results Scanning Electron Microscopy analysis of the fungal treated LDPE films provided a solid evidence of biodegradation. Fungi were identified as Aspergillus spp. LDPE degradation is a severe environmental crisis in the world and we have proved that microorganisms can be used for bioremediation in this line. Key words: Biodegradation, low density polyethylene (LDPE), Aspergillus, marine fungi, Sturm test.

Abstract: Intimate coupling of photocatalysis and biodegradation (ICPB) offers potential for degrading biorecalcitrant and toxic organic compounds. This study reports on a novel sponge-type, TiO(2)-coated biofilm carrier that showed significant adherence of TiO(2) and ability to accumulate biomass in its interior. This carrier was tested for ICPB in a continuous-flow photocatalytic circulating-bed biofilm reactor (PCBBR) to mineralize 2,4,5-trichlorophenol (TCP), which is biorecalcitrant. Four mechanisms possibly acting in ICPB were tested separately: TCP adsorption to the carrier, UV photolysis, UV photocatalysis, and biodegradation by biofilm inside the carrier. The carrier exhibited strong TCP adsorption that followed a Freundlich isotherm with an exponent near 2. Whereas UV photolysis was negligible, photocatalysis produced TCP-degradation products that could be mineralized, and the strong adsorption of TCP to the carrier enhanced biodegradation by relieving toxicity. Validating the ICPB concept, biofilm was protected inside the carriers, although biomass originally on the outer surface of the carriers was eliminated. ICPB significantly lowered the diversity of the bacterial community, but five genera known to biodegrade chlorinated phenols (Ralstonia, Bradyrhizobium, Methylobacterium, Cupriavidus, and Pandoraea) were markedly enriched.

Abstract: This work aimed at evaluating the biodegradability of different bacterial surfactants in liquid medium and in soil microcosms. The biodegradability of biosurfactants by pure and mixed bacterial cultures was evaluated through CO2 evolution. Three bacterial strains, Acinetobacter baumanni LBBMA ES11, Acinetobacter haemolyticus LBBMA 53 and Pseudomonas sp. LBBMA 101B, used the biosurfactants produced by Bacillus sp. LBBMA 111A (mixed lipopeptide), Bacillus subtilis LBBMA 155 (lipopeptide), Flavobacterium sp. LBBMA 168 (mixture of flavolipids), Dietzia Maris LBBMA 191(glycolipid) and Arthrobacter oxydans LBBMA 201(lipopeptide) as carbon sources in minimal medium. The synthetic surfactant sodium dodecyl sulfate (SDS) was also mineralized by these microorganisms, but at a lower rate. CO2 emitted by a mixed bacterial culture in soil microcosms with biosurfactants was higher than in the microcosm containing SDS. Biosurfactant mineralization in soil was confirmed by the increase in surface tension of the soil aqueous extracts after incubation with the mixed bacterial culture. It can be concluded that, in terms of biodegradability and environmental security, these compounds are more suitable for applications in remediation technologies in comparison to synthetic surfactants. However, more information is needed on structure of biosurfactants, their interaction with soil and contaminants and scale up and cost for biosurfactant production.

Abstract: In this study, polyvinyl alcohol (PVOH)/corn starch (CS) blend films were prepared using the solution casting method. The biodegradability of the films was investigated based on enzymatic absorbency in water and an acidic solution as well as by burial in soil and compost. The tensile properties were examined using a tensile test. The structure of the film was characterised by scanning electron microscopy. Compared to a film without corn starch, the films containing corn starch were found to be more highly biodegradable by enzymes as well as in soil and compost. However, the results from the tensile and elongation at break tests showed that as the corn starch content increased, the strength decreased. The morphology study revealed the distribution of corn starch in the PVOH.

Abstract: Combined processes of biological anaerobic baffled reactor (ABR) and UV/H2O2 at a laboratory scale were studied to treat a synthetic slaughterhouse wastewater. In this study, the total organic carbon (TOC) loadings of 0.2–1.1 g/(L day) were used. The results revealed that combined processes had a higher efficiency to treat the synthetic slaughterhouse wastewater. Up to 95% TOC removal was obtained for an influent concentration of 973.3 mgTOC/L at the hydraulic retention time (HRT) of 3.8 days in the ABR and 3.6 h in the UV photoreactor. Meanwhile, up to 97.7% and 96.6% removal of chemical oxygen demand (COD) and 5-day carbonaceous biochemical oxygen demand (CBOD5) were observed in the ABR for the same influent concentration, respectively. Comparatively, for an influent concentration of 157.6 mgTOC/L, the UV/H2O2 process alone with the TOC loading of 0.06–1.9 g/(L h) was also studied, in which, up to 64.3%, 83.7%, and 84.3% of TOC, COD, and CBOD5 removal were observed, respectively, at the HRT of 2.5 h with hydrogen peroxide (H2O2) concentration of 529 mg/L. It was found that individual ABR and UV/H2O2 processes enhanced the biodegradability of the treated effluent by an increased CBOD5/COD ratio of 0.4 to 0.6. An optimum H2O2 dosage of 3.5 (mgH2O2)/(mgTOCin h) was also found for the UV/H2O2 process.

Abstract: In order to demonstrate the potentials of both bioenergy production and microcystin (MC) biodegradation in methanogenic conditions, the biogas production, process stability and the variation of MC concentration in anaerobic digestion of blue algae from Taihu Lake were studied. A methane yield of 189.89 mL g−1 VS was obtained from the digester, and the average methane concentration in the biogas was 36.72%. During the digestion, the pH value was fairly constant (6.8 to 7.6), and soluble chemical oxygen demand (SCOD) kept at a relatively stable level. The concentration of total volatile fatty acid (VFA) increased significantly in the first 8 days, and then decreased, showing no inhibition on the digestion. The results also showed that the concentration of MC could be significantly reduced from 1220.19 μg L−1 to 35.17 μg L−1 during the methanogenic process, which followed the first order kinetics well. These findings suggest that anaerobic digestion of blue algae can both generate renewable energy biogas and lead to biodegradation of MC, presenting significant potentials for bioremediation of MC and post-treatment of blue algae.

Abstract: Biodegradation of poorly water-soluble liquid hydrocarbons is often limited by low availability of the substrate to microbes. Adhesion of microorganisms to an oil–water interface can enhance this availability, whereas detaching cells from the interface can reduce the rate of biodegradation. The capability of microbes to adhere to the interface is not limited to hydrocarbon degraders, nor is it the only mechanism to enable rapid uptake of hydrocarbons, but it represents a common strategy. This review of the literature indicates that microbial adhesion can benefit growth on and biodegradation of very poorly water-soluble hydrocarbons such as n-alkanes and large polycyclic aromatic hydrocarbons dissolved in a non-aqueous phase. Adhesion is particularly important when the hydrocarbons are not emulsified, giving limited interfacial area between the two liquid phases. When mixed communities are involved in biodegradation, the ability of cells to adhere to the interface can enable selective growth and enhance bioremediation with time. The critical challenge in understanding the relationship between growth rate and biodegradation rate for adherent bacteria is to accurately measure and observe the population that resides at the interface of the hydrocarbon phase.

Abstract: This study deals with production and characterization of biosurfactant from renewable resources by Pseudomonas aeruginosa. Biosurfactant production was carried out in 3L fermentor using waste motor lubricant oil and peanut oil cake. Maximum biomass (11.6 mg/ml) and biosurfactant production (8.6 mg/ml) occurred with peanut oil cake at 120 and 132 h respectively. Characterization of the biosurfactant revealed that, it is a lipopeptide with chemical composition of protein (50.2%) and lipid (49.8%). The biosurfactant (1 mg/ml) was able to emulsify waste motor lubricant oil, crude oil, peanut oil, kerosene, diesel, xylene, naphthalene and anthracene, comparatively the emulsification activity was higher than the activity found with Triton X-100 (1 mg/ml). Results obtained in the present study showed the possibility of biosurfactant production using renewable, relatively inexpensive and easily available resources. Emulsification activity found with the biosurfactant against different hydrocarbons showed its possible application in bioremediation of environments polluted with various hydrocarbons.