Tan Suet May Amelia

Polylactic acid (PLA) is a bio-based polymer known to exhibit only thermophilic compostability. We recently developed a unique set of compost that can biodegrade PLA at mesophilic conditions, and it exhibited more than 10-fold higher PLA breakdown activity than control composts. Here, we investigated the potential selection of bioactivities related to PLA breakdown in our uniquely trained compost and surveyed the occurrences of those activities in a range of terrestrial and marine environments for comparison. We found that the fraction of PLA-hydrolyzing bacteria in our trained compost was not significantly increased compared to environmental samples. However, PLA-clearing strains isolated from the trained compost were twice as efficient in hydrolyzing PLA compared to those derived from environmental soil, indicating that our trained compost had undergone selection of strains with higher hydrolysis activity. This provides an important insight into PLA-related bioactivity in our trained compost, and it further suggests additional bioactivities that facilitate PLA breakdown most likely exist in our trained compost. Our findings support a multi-step model for mesophilic PLA composting in which several microbial-based bioactivities act synergistically to enhance PLA biodegradation. IMPORTANCE: We recently succeeded in developing a unique trained compost that can biodegrade the most common bioplastic, polylactic acid (PLA), by overcoming the high-temperature condition previously thought to be required for PLA biodegradation. In this present study, we investigated bioactivities in this trained compost of ours to understand how mesophilic PLA composting could be achieved, and we found that there was selection of more efficient PLA-hydrolyzing strains in the trained compost. Notably, PLA compostability in our trained compost is much higher than that in controls, and this cannot be fully explained by the increase in PLA hydrolysis activity alone, strongly suggesting that there are additional bioactivities in the trained compost that facilitate PLA breakdown. Therefore, we propose that mesophilic PLA biodegradation requires the collective action of several distinct microbial activities.

Polylactic acid (PLA) is a polymer that is known to exhibit compostability at thermophilic temperatures, and this activity is thought to be connected to the presence of PLA hydrolyzability in environmental microbes. We recently developed a set of compost that can biodegrade PLA at mesophilic conditions, and one possible reason underlying our success could be due to the enrichment of PLA hydrolyzability. Here, we investigated the potential selection of bioactivities related to PLA breakdown in our trained compost and surveyed the occurrences of those activities in the environment for comparison. Ten different environments were sampled, including PLA, larval gut of black soldier flies, and organic material from our trained compost, as well as terrestrial soil, estuarine sediment, brackish water, shell biofilm, coastal stranded polystyrene, bottle, and bottle cap. We found a small fraction of cultivable bacteria in many samples that harbored PLA degradability. For our trained compost, PLA-degrading isolates were twice as efficient as those from other environments, even though the frequency at which they were detected was not significantly higher. These findings suggested that PLA breakdown ability is commonly present at a low percentage in most environments, and that our trained compost has been able to select for more effective isolates. As this enhancement is likely insufficient to explain the increase in PLA compostability in our trained compost compared to standard mesophilic composts, we propose that additional microbial activities are needed to act synergistically and overcome the requirement for elevated temperature in PLA composting. IMPORTANCE: This study represents our work in investigating the biodegradation activity of the most common bioplastic, PLA, in the environment and in a special compost we recently developed that exhibited the novel ability of being able to achieve PLA composting at ambient temperatures. Our work is a rare survey that compares PLA hydrolytic activity across different environments, helping unmask the underlying prevalence of environmental PLA hydrolysis activity, as well as whether our special compost is especially enriched for such activity, would facilitate the design of PLA biodegradation implementation strategies. We found that PLA hydrolytic activity was generally present in environmental microbes at low frequencies, and that our special compost selected for those that were more efficient. However, full PLA compostability under mesophilic conditions likely depends on embedded, synergistic microbial functions beyond hydrolysis alone, motivating future work to disentangle complementary activities that collectively enable complete breakdown.

Polyhydroxyalkanoate (PHA), a biodegradable and plastic-like biopolymer, has been receiving research and industrial attention due to severe plastic pollution, resource depletion, and global waste issues. This has spurred the isolation and characterisation of novel PHA-producing strains through cultivation and non-cultivation approaches, with a particular interest in genes encoding PHA synthesis pathways. Since sea sponges and sediment are marine benthic habitats known to be rich in microbial diversity, sponge tissues (Xestospongia muta and Aaptos aaptos) and sediment samples were collected in this study from Redang and Bidong islands located in the Malaysian Coral Triangle region. PHA synthase (phaC) genes were identified from sediment-associated bacterial strains using a cultivation approach and from sponge-associated bacterial metagenomes using a non-cultivation approach. In addition, phylogenetic diversity profiling was performed for the sponge-associated bacterial community using 16S ribosomal ribonucleic acid (16S rRNA) amplicon sequencing to screen for the potential presence of PHA-producer taxa. A total of three phaC genes from the bacterial metagenome of Aaptos and three phaC genes from sediment isolates (Sphingobacterium mizutaii UMTKB-6, Alcaligenes faecalis UMTKB-7, Acinetobacter calcoaceticus UMTKB-8) were identified. Produced PHA polymers were shown to be composed of 5C to nC monomers, with previously unreported PHA-producing ability of the S. mizutaii strain, as well as a 3-hydroxyvalerate-synthesising ability without precursor addition by the A. calcoaceticus strain.

Polyhydroxyalkanoates (PHA) are biodegradable polymers that are considered able to replace synthetic plastic because their biochemical characteristics are in some cases the same as other biodegradable polymers. However, due to the disadvantages of costly and non-renewable carbon sources, the production of PHA has been lower in the industrial sector against conventional plastics. At the same time, first-generation sugar-based cultivated feedstocks as substrates for PHA production threatens food security and considerably require other resources such as land and energy. Therefore, attempts have been made in pursuit of suitable sustainable and affordable sources of carbon to reduce production costs. Thus, in this review, we highlight utilising waste lignocellulosic feedstocks (LF) as a renewable and inexpensive carbon source to produce PHA. These waste feedstocks, second-generation plant lignocellulosic biomass, such as maize stoves, dedicated energy crops, rice straws, wood chips, are commonly available renewable biomass sources with a steady supply of about 150 billion tonnes per year of global yield. The generation of PHA from lignocellulose is still in its infancy, hence more screening of lignocellulosic materials and improvements in downstream processing and substrate pre-treatment are needed in the future to further advance the biopolymer sector.

For many decades, global efforts have been attempted to replace the petrochemical plastics with biodegradable and environment friendly plastics. The petrochemical plastics that require many years to decompose have profound consequences on the environment. A natural, biodegradable, and plastic‐like polymer, polyhydroxyalkanoate (PHA), has been extracted from and synthesized by microbes, particularly bacteria. However, the prospective large‐scale production of PHA faced an economic bottleneck for less production costs. Research has thus shifted to one of the most common alternatives, which is the utilization of less costly raw materials or carbon sources that include industrial by‐products and wastes, such as glycerine pitch and glycerol. This review elucidates the discovery, basic mechanisms, and applications of PHA, as well as provides insights regarding the importance of PHA conversion from glycerine pitch and glycerol. This review also summarizes some possible future modifications to improve the efficiency of glycerine pitch and glycerol as carbon sources in PHA production. The conversion endeavors of wastes to a valuable product, PHA, that not only reduces petrochemical plastic pollution, waste generation, and PHA production costs but also supports economic and resource sustainability, which ultimately further progress towards the cradle‐to‐cradle design and circular bioeconomy concept.

Nanobiotechnology has undoubtedly influenced major breakthroughs in medical sciences. Application of nanosized materials has made it possible for researchers to investigate a broad spectrum of treatments for diseases with minimally invasive procedures. Silver nanoparticles (AgNPs) have been a subject of investigation for numerous applications in agriculture, water treatment, biosensors, textiles, and the food industry as well as in the medical field, mainly due to their antimicrobial properties and nanoparticle nature. In general, AgNPs are known for their superior physical, chemical, and biological properties. The properties of AgNPs differ based on their methods of synthesis and to date, the biological method has been preferred because it is rapid, nontoxic, and can produce well-defined size and morphology under optimized conditions. Nevertheless, the common issue concerning biological or biobased production is its sustainability. Researchers have employed various strategies in addressing this shortcoming, such as recently testing agricultural biowastes such as fruit peels for the synthesis of AgNPs. The use of biowastes is definitely cost-effective and eco-friendly; moreover, it has been reported that the reduction process is simple and rapid with reasonably high yield. This review aims to address the developments in using fruit- and vegetable-based biowastes for biologically producing AgNPs to be applied as antimicrobial coatings in biomedical applications.

Microplastic pollutes water, land, air, and groundwater environments not only visually but also ecologically for plants, animals, and humans. Microplastic has been reported to act as vectors by sorbing pollutants and contributing to the bioaccumulation of pollutants, particularly in marine ecosystems, organisms, and subsequently food webs. The inevitable exposure of microplastic to humans emphasises the need to review the potential effects, exposure pathways, and toxicity of microplastic toward human health. Therefore, this review was aimed to reveal the risks of pollutant sorption and bioaccumulation by microplastic toward humans, as well as the dominant types of pollutants sorbed by microplastic, and the types of pollutants that are bioaccumulated by microplastic in the living organisms of the marine ecosystem. The possible factors influencing the sorption and bioaccumulation of pollutants by microplastic in marine ecosystems were also reviewed. The review also revealed the prevailing types of microplastic, abundance of microplastic, and geographical distribution of microplastic in the aquatic environment globally. The literature review revealed that microplastic characteristics, chemical interactions, and water properties played a role in the sorption of pollutants by microplastic. The evidence of microplastic posing a direct medical threat to humans is still lacking albeit substantial literature has reported the health hazards of microplastic-associated monomers, additives, and pollutants. This review recommends future research on the existing knowledge gaps in microplastic research, which include the toxicity of microplastic, particularly to humans, as well as the factors influencing the sorption and bioaccumulation of pollutants by microplastic.

Polyhydroxyalkanoates (PHAs) are bacteria derived bio-based polymers that are synthesised under limited conditions of nutritional elements with excess carbon sources. Among the members of PHAs, poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [(P(3HB-co-4HB)] emerges as an attractive biomaterial to be applied in medical applications owing to its desirable mechanical and physical properties, non-genotoxicity and biocompatibility eliciting appropriate host tissue responses. The tailorable physical and chemical properties and easy surface functionalisation of P(3HB-co-4HB) increase its practicality to be developed as functional medical substitutes. However, its applicability is sometimes limited due to its hydrophobic nature due to fewer bio-recognition sites. In this review, we demonstrate how surface modifications of PHAs, mainly P(3HB-co-4HB), will overcome these limitations and facilitate their use in diverse medical applications. The integration of nanotechnology has drastically enhanced the functionality of P(3HB-co-4HB) biomaterials for application in complex biological environments of the human body. The design of versatile P(3HB-co-4HB) materials with surface modifications promise a non-cytotoxic and biocompatible material without inducing severe inflammatory responses for enhanced effective alternatives in healthcare biotechnology. The enticing work carried out with P(3HB-co-4HB) promises to be one of the next-generation materials in biomedicines which will facilitate translation into the clinic in the future.