Advances in methods for detecting plastics biodegradation / 生物工程学报

The pollution caused by improper handling of plastics has become a global challenge. In addition to recycling plastics and using biodegradable plastics, an alternative solution is to seek efficient methods for degrading plastics. Among them, the methods of using biodegradable enzymes or microorganisms to treat plastics have attracted increasing attention because of its advantages of mild conditions and no secondary environmental pollution. Developing highly efficient depolymerizing microorganisms/enzymes is the core for plastics biodegradation. However, the current analysis and detection methods cannot meet the requirements for screening efficient plastics biodegraders. It is thus of great significance to develop rapid and accurate analysis methods for screening biodegraders and evaluating biodegradation efficiency. This review summarizes the recent application of various commonly used analytical techniques in plastics biodegradation, including high performance liquid chromatography, infrared spectroscopy, gel permeation chromatography, and determination of zone of clearance, with fluorescence analysis techniques highlighted. This review may facilitate standardizing the characterization and analysis of plastics biodegradation process and developing more efficient methods for screening plastics biodegraders.

Producción de plásticos biodegradables a partir de bacterias de hábitats salinos aisladas de la Laguna de Ayarza / Production of biodegradable plastics from saline habitats bacteria isolated from Laguna de Ayarza

La contaminación por plásticos petroquímicos es una grave amenaza para el medio ambiente que requiere im-plementar alternativas como los bioplásticos para lograr un desarrollo sostenible. Los polihidroxialcanoatos (PHA) son polímeros utilizados para la producción de plásticos biodegradables y que han llamado la atención como sustitutos de los plásticos de base fósil. Sin embargo, el costo de producción de los PHA constituye una barrera para su producción industrial a gran escala. Las de bacterias de hábitats salinos son microorganismos prometedores para la síntesis de PHA debido a sus características tales como altos requisitos de salinidad que previenen la contaminación microbiana, la alta presión osmótica intracelular que permite una fácil lisis celular para purificar los PHA y la capacidad para usar un amplio espectro de sustratos. La presente investigación planteó determinar las cepas nativas de bacterias halófilas y halotolerantes de la Laguna de Ayarza capaces de producir PHA, establecer la capacidad que tienen de utilizar residuos agrícolas para la producción de PHA y determinar su eficiencia. Esto se logró a través de la inoculación de las cepas productoras de PHA en medios de fermentación con pulpa de café, cáscaras de plátanos y salvado de trigo lo que permitió determinar las cepas más eficientes. Se encontró que las bacterias productoras de PHA pertenecen a las especies: Alcaligenes faecalis, Bacillus idriensis, Bacillus megaterium, Exiguobacterium acetylicum, E. aurantiacum, Pseudomonas cuatrocienegasensis y Sta-phylococcus capitis y que las cepas AP21-14, AP21-10 y AP21-03 mostraron los mejores resultados que podrían ser prometedores para la producción a nivel industrial.

Pollution by petrochemical plastics is a serious threat to the environment that requires the implementation of al-ternatives such as bioplastics to achieve sustainable development. Polyhydroxyalkanoates (PHAs) are polymers used for the production of biodegradable plastics and have drawn attention as substitutes for fossil-based plastics. However, the cost of producing PHAs constitutes a barrier to their large-scale industrial production. Bacteria from saline environments bacteria are promising microorganisms for PHA synthesis due to their characteristics such as high salinity requirements that prevent microbial contamination, high intracellular osmotic pressure that allows easy cell lysis to purify PHAs, and the ability to use a broad spectrum of substrates. This research project aimed to determine the native strains of halophilic and halotolerant bacteria from Laguna de Ayarza capable of producing PHA, establish their ability to use agricultural residues for the production of PHA, and determine their efficiency. This was achieved through the inoculation of the PHA-producing strains in fermentation media with coffee pulp, banana peels and wheat bran, which allowed determining the most efficient strains. It was found that the PHA-producing bacteria belong to the species: Alcaligenes faecalis, Bacillus idriensis, Bacillus mega-terium, Exiguobacterium acetylicum, E. aurantiacum, Pseudomonas cuatrocienegasensis and Staphylococcus capitis and that the strains AP21-14, AP21-10 and AP21-03 showed the best results that could be promising for production at an industrial level.

Castor Bean Cake Protein-based Biodegradable Films: Gallic Acid Effect

Abstract: The objective of this work was to evaluate the effect of gallic acid (GA) concentration on some physical properties and biodegradability of films produced with proteins extracted from the castor bean cake. The films, prepared by the casting technique, showed homogeneous and brownish appearance. As the GA concentration increased (from 0 to 10 g/100 g protein), the films gradually became darker and more opaque; while the gloss had few significant differences. Solubility, tensile strength and elasticity modulus values of films varied due to changing concentrations of gallic acid. Elongation at break and water vapor permeability values did not have significant changes. A 60% mineralization value of the film containing GA was obtained at 21 days, evidencing its biodegradability. These dark and opaque films could be used in agriculture, specifically in seedling bags as the dark color decrease the incidence of light, preventing root weakening, and the seedlings can be transplanted directly without removal of the film.