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Acrylic polymers (AP) are a diverse group of materials with broad applications, frequent use, and increasing demand. Some of the most used AP are polyacrylamide, polyacrylic acid, polymethyl methacrylates, and polyacrylonitrile. Although no information for the production of all AP types is published, data for the most used AP is around 9 MT/year, which gives an idea of the amount of waste that can be generated after products' lifecycles. After its lifecycle ends, the fate of an AP product will depend on its chemical structure, the environmental setting where it was used, and the regulations for plastic waste management existing in the different countries. Even though recycling is the best fate for plastic polymer wastes, few AP can be recycled, and most of them end up in landfills. Because of the pollution crisis the planet is immersed, setting regulations and developing technological strategies for plastic waste management are urgent. In this regard, biotechnological approaches, where microbial activity is involved, could be attractive eco-friendly strategies. This mini-review describes the broad AP diversity, their properties and uses, and the factors affecting their biodegradability, underlining the importance of standardizing biodegradation quantification techniques. We also describe the enzymes and metabolic pathways that microorganisms display to attack AP chemical structure and predict some biochemical reactions that could account for quaternary carbon-containing AP biodegradation. Finally, we analyze strategies to increase AP biodegradability and stress the need for more studies on AP biodegradation and developing stricter legislation for AP use and waste control. Key points: • Acrylic polymers (AP) are a diverse and extensively used group of compounds. • The environmental fates and health effects of AP waste are not completely known. • Microorganisms and enzymes involved in AP degradation have been identified. • More biodegradation studies are needed to develop AP biotechnological treatments. [ABSTRACT FROM AUTHOR]

Cutinase-like esterase from the yeasts Pseudozyma antarctica (PaE) shows strong degradation activity in an agricultural biodegradable plastic (BP) model of mulch films composed of poly(butylene succinate- co-adipate) (PBSA). P. antarctica is known to abundantly produce a glycolipid biosurfactant, mannosylerythritol lipid (MEL). Here, the effects of MEL on PaE-catalyzed degradation of BPs were investigated. Based on PBSA dispersion solution, the degradation of PBSA particles by PaE was inhibited in the presence of MEL. MEL behavior on BP substrates was monitored by surface plasmon resonance (SPR) using a sensor chip coated with polymer films. The positive SPR signal shift indicated that MEL readily adsorbed and spread onto the surface of a BP film. The amount of BP degradation by PaE was monitored based on the negative SPR signal shift and was decreased 1.7-fold by MEL pretreatment. Furthermore, the shape of PBSA mulch films in PaE-containing solution was maintained with MEL pretreatment, whereas untreated films were almost completely degraded and dissolved. These results suggest that MEL covering the surface of BP film inhibits adsorption of PaE and PaE-catalyzed degradation of BPs. We applied the above results to control the microbial degradation of BP mulch films. MEL pretreatment significantly inhibited BP mulch film degradation by both PaE solution and BP-degradable microorganism. Moreover, the degradation of these films was recovered after removal of the coated MEL by ethanol treatment. These results demonstrate that the biodegradation of BP films can be readily and reversibly controlled by a physical approach using MEL. [ABSTRACT FROM AUTHOR]

The development of biodegradable plastic mulch films for use in agriculture has been ongoing for decades. These films consist of mixtures of polymers with various additives. As a result, their physical and chemical properties differ from those of the pure polymers often used for in vitro enzymatic and microbial degradation studies, raising questions about the biodegradation capability of mulch films. Currently, standards exist for the biodegradation of plastics in composting conditions but not in soil. Biodegradation in soil or compost depends on a complex synergy of biological and abiotic degradative processes. This review discusses the physicochemical and structural properties of biodegradable plastic mulches, examines their potential for on-site decomposition in light of site-to-site variance due to environmental and biological conditions, and considers the potential for long-term effects on agroecosystem sustainability and functionality. [ABSTRACT FROM AUTHOR]

Here, we report the use of petrochemical aromatic hydrocarbons as a feedstock for the biotechnological conversion into valuable biodegradable plastic polymers—polyhydroxyalkanoates (PHAs). We assessed the ability of the known Pseudomonas putida species that are able to utilize benzene, toluene, ethylbenzene, p-xylene (BTEX) compounds as a sole carbon and energy source for their ability to produce PHA from the single substrates. P. putida F1 is able to accumulate medium-chain-length (mcl) PHA when supplied with toluene, benzene, or ethylbenzene. P. putida mt-2 accumulates mcl-PHA when supplied with toluene or p-xylene. The highest level of PHA accumulated by cultures in shake flask was 26% cell dry weight for P. putida mt-2 supplied with p-xylene. A synthetic mixture of benzene, toluene, ethylbenzene, p-xylene, and styrene (BTEXS) which mimics the aromatic fraction of mixed plastic pyrolysis oil was supplied to a defined mixed culture of P. putida F1, mt-2, and CA-3 in the shake flasks and fermentation experiments. PHA was accumulated to 24% and to 36% of the cell dry weight of the shake flask and fermentation grown cultures respectively. In addition a three-fold higher cell density was achieved with the mixed culture grown in the bioreactor compared to shake flask experiments. A run in the 5-l fermentor resulted in the utilization of 59.6 g (67.5 ml) of the BTEXS mixture and the production of 6 g of mcl-PHA. The monomer composition of PHA accumulated by the mixed culture was the same as that accumulated by single strains supplied with single substrates with 3-hydroxydecanoic acid occurring as the predominant monomer. The purified polymer was partially crystalline with an average molecular weight of 86.9 kDa. It has a thermal degradation temperature of 350 °C and a glass transition temperature of −48.5 °C. [ABSTRACT FROM AUTHOR]

Poly-3-hydroxyalkanoates [P(3HA)s] are biologically produced polyesters that have attracted much attention as biodegradable polymers that can be produced from biorenewable resources. These polymers have many attractive properties for use as bulk commodity plastics, fishing lines, and medical uses that are dependent on the repeating unit structures. Despite the readily apparent benefits of using P(3HA)s as replacements for petrochemical-derived plastics, the use and distribution of P(3HA)s have been limited by their cost of production. This problem is currently being addressed by the engineering of enzymes involved in the production of P(3HA)s. Polyhydroxyalkanoate (PHA) synthase (PhaC) enzymes, which catalyze the polymerization of 3-hydroxyacyl-CoA monomers to P(3HA)s, were subjected to various forms of protein engineering to improve the enzyme activity or substrate specificity. This review covers the recent history of PHA synthase engineering and also summarizes studies that have utilized engineered PHA synthases. [ABSTRACT FROM AUTHOR]