An analytical review on revamping plastic waste management: exploring recycling, biodegradation, and the growing role of biobased plastics.

Globally, 90% of plastics are synthetic, made up of crude oil, natural gas, and coal. Even though plastic is extremely useful in our lives, its excessive use and mismanaged disposal are negatively affecting the ecosystem. The review highlights that the recycling process plays a critical role in controlling the problem of plastic pollution. Although plastic recycling is the most common approach used for managing plastic waste, only 2% of the total plastic waste enters the closed-loop system. However, the review suggests that along with recycling, cost-effective and environmentally friendly plastic approaches can synergistically help to control this increasing problem of plastic waste accumulation. The review further discusses the consequences of plastic pollution on humans and the environment. In particular, the review focuses on biocatalytic and bioengineering tools for the degradation of polyethylene terephthalate (PET), one of the major contributors to plastic waste in landfills and oceans. Moreover, the review presents biobased and biodegradable materials, derived from renewable feedstocks, as an alternative to petroleum-based plastics along with their complete end-of-life options. Overall, this review analyzes the current scenario of the plastic industry, from plastic production to waste generation and management, loopholes and challenges in the current management strategies, and possible solutions like recycling, biodegradation, and biobased plastics.

Perceiving biobased plastics as an alternative and innovative solution to combat plastic pollution for a circular economy.

Plastic waste from fossil-based sources, including single-use packaging materials, is continuously accumulating in landfills, and leaching into the environment. A 2021 UN Environment Programme (UNEP) report suggests that the plastic pollution is likely to be doubled by 2030, posing a major challenge to the environment and the overall global plastic waste management efforts. The use of biobased plastics such as polyhydroxyalkanoates (PHAs) as a biodegradable substitute for petroleum-based plastics could be a feasible option to combat this issue which may further result in much lower carbon emissions and energy usage in comparison to conventional plastics as additional advantages. Though recent years have seen the use of microbes as biosynthetic machinery for biobased plastics, using various renewable feedstocks, the scaled-up production of such materials is still challenging. The current study outlays applications of biobased plastics, potential microorganisms producing biobased plastics such as Cupriavidus necator, Bacillus sp., Rhodopseudomonas palustris, microalgae, and mixed microbial cultures, and inexpensive and renewable resources as carbon substrates including industrial wastes. This review also provides deep insights into the operational parameters, challenges and mitigation, and future opportunities for maximizing the production of biobased plastic products. Finally, this review emphasizes the concept of biorefinery as a sustainable and innovative solution for biobased plastic production for achieving a circular bioeconomy.

Framework to improve biohydrogen generation with estrogen co-metabolism under complete suppression of nitrogen source.

The current work provides insights for improving the hydrogen output while degrading emerging contaminants using Rhodopseudomonas palustris. The changes in the growth rate of a microorganism due to different substrate inputs affects the hydrogen production due to metabolic route changes. The different ratios of glutamate and glycerol as nitrogen and carbon sources along with the presence of ethinylestradiol (EE2) in the photofermenter affected the flux of electrons being directed towards biosynthesis and biohydrogen generation. The combination of glutamate and glycerol in different ratios (Glu:Gly; 0, 0.20 and 0.54) along with estrogen showed no significant difference in the bacteriochlorophyll concentrations. The highest biomass concentration (0.013 h-1) was in ratio of 0.54 while maximum specific hydrogen production (1.9 ± 0.05 ml g-1 biomass h-1) was observed under complete suppression of nitrogen (0; without Glu; non-growing condition) with resultant improved estrogen degradation of about 78% in 168 h by R. palustris strain MDOC01.