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.

Microbial Biofilms for Environmental Bioremediation of Heavy Metals: a Review.

Heavy metal pollution caused due to various industrial and mining activities poses a serious threat to all forms of life in the environment because of the persistence and toxicity of metal ions. Microbial-mediated bioremediation including microbial biofilms has received significant attention as a sustainable tool for heavy metal removal as it is considered safe, effective, and feasible. The biofilm matrix is dynamic, having microbial cells as major components with constantly changing and evolving microenvironments. This review summarizes the bioremediation potential of bacterial biofilms for different metal ions. The composition and mechanism of biofilm formation along with interspecies communication among biofilm-forming bacteria have been discussed. The interaction of biofilm-associated microbes with heavy metals takes place through a variety of mechanisms. These include biosorption and bioaccumulation in which the microbes interact with the metal ions leading to their conversion from a highly toxic form to a less toxic form. Such interactions are facilitated via the negative charge of the extracellular polymeric substances on the surface of the biofilm with the positive charge of the metal ions and the high cell densities and high concentrations of cell-cell signaling molecules within the biofilm matrix. Furthermore, the impact of the anodic and cathodic redox potentials in a bioelectrochemical system (BES) for the reduction, removal, and recovery of numerous heavy metal species provides an interesting insight into the bacterial biofilm-mediated bioelectroremediation process. The review concludes that biofilm-linked bioremediation is a viable option for the mitigation of heavy metal pollution in water and ecosystem recovery.

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.

Biodegradation of synthetic estrogen using bioelectrochemical system and degradation pathway analysis through Quadrupole-time-of-flight-mass spectrometry.

Synthetic estrogenic compounds such as 17α-ethinylestradiol (EE2) are significant environmental contaminants. This research studied the biodegradation of EE2 utilizing the EE2 adapted cells isolated from a dairy farm waste site in suspension flask vis-a-vis Bioelectrochemical System (BES) and compared the power output in the BES with and without EE2 as a co-substrate. 78% removal of EE2 was observed in the BES as against 60% removal in suspension flasks. The maximum power density in the BES increased about 53% when EE2 is used as a co-substrate. The EE2 biodegradation studied using HPLC and Q-TOF methods, also proposes a hypothetical pathway for EE2 degradation by the newly isolated strain Rhodopseudomonas palustris MDOC01 and reports the significant metabolites like nicotinic acid and oxoproline being detected during bioelectrochemical treatment process of EE2. Study also suggests that Plasma peroxide treatment of anode material enhanced the overall performance in terms of biodegradation efficiency and power output.

Effect of earthworms in reduction and fate of antibiotic resistant bacteria (ARB) and antibiotic resistant genes (ARGs) during clinical laboratory wastewater treatment by vermifiltration.

In the recent decades, the role of wastewater treatment plants has been entrenched for the dissemination of antibiotic resistant bacteria into the environment. The present study explores the dynamics of earthworms-microorganisms interactions involved in the high treatment efficacy of vermifiltration technology along with reduction of antibiotic resistant bacteria (ARB). This study is the first of its kind to investigate the performance efficacy of vermifilter (VF) for clinical laboratory wastewater treatment. The results of the study showed that earthworms and VF associated microbial community had a significant effect on Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) reduction (78-85%), coliforms and pathogen removal (>99.9%) and caused a significant shift in the prevalence pattern of ARB. Molecular profiling of resistance causing genes such as ESBL (blaSHV, blaTEM and blaCTX-M), MRSA (mec-A) and Colistin (mcr-1) confirmed the probable mechanisms behind the resistance pattern. The microbial community diversity in the influent, earthworm's coelomic fluid and gut and filter media layers associated with the VF assists in the formation of biofilm, which helps in the removal of pathogens from the wastewater. This biofilm formation further results in a paradigm shift in the resistance profile of ARB and ARG, specifically most effective against drugs, targeting cell wall and protein synthesis inhibition such as Ampicillin, Ticarcillin, Gentamicin and Chloramphenicol. These findings further validate vermifiltration technology as a sustainable and natural treatment technology for clinical laboratory wastewater, specifically for the removal of pathogens and antibiotic resistance.

Sewage surveillance for the presence of SARS-CoV-2 genome as a useful wastewater based epidemiology (WBE) tracking tool in India.

The infection with SARS-CoV-2 is reported to be accompanied by the shedding of the virus in fecal samples of infected patients. Earlier reports have suggested that COVID-19 agents can be present in the sewage samples and thus it can be a good indication of the pandemic extent in a community. However, no such studies have been reported in the Indian context. Hence, it becomes absolutely necessary to detect the presence of the SARS-CoV-2 in the wastewater samples from wastewater treatment plants (WWTPs) serving different localities of Jaipur city. Samples from different WWTPs and hospital wastewater samples were collected and wastewater based epidemiology (WBE) studies were carried out using the RT-PCR to confirm the presence of different COVID-19 target genes namely S gene, E gene, ORF1ab gene, RdRp gene and N gene. The results revealed that the untreated wastewater samples showed the presence of SARS-CoV-2 viral genome, which was correlated with the increased number of COVID-19 positive patients from the concerned areas, as reported in the publically available health data. This is the first study that investigated the presence of SARS-CoV-2 viral genome in wastewater, at higher ambient temperature (45 °C), further validating WBE as potential tool in predicting and mitigating outbreaks.