Characterization of a polyhydroxyalkanoate obtained from pineapple peel waste using Ralsthonia eutropha

Biodegradation of terephthalic acid using Rhodococcus erythropolis MTCC 3951: Insights into the degradation process, applications in wastewater treatment and polyhydroxyalkanoate production

Terephthalic acid (TPA) is an endocrine disruptor widely used as a plasticizer and as a monomer in the manufacturing of PET bottles. However, because of various harmful effects on humans and the environment, it is now recognized as a priority pollutant whose environmental level needs to be controlled. In the present work, the TPA biodegradation efficacy of the bacterium Rhodococcus erythropolis (MTCC 3951) was studied in mineral salt media with TPA as the sole carbon and energy source. R. erythropolis was observed to degrade 5 mM and 120 mM TPA within 10 h and 84 h of incubation, respectively. The degradation efficiency was further optimized by varying the culture conditions, and the following optimum conditions were obtained: inoculum size- 5% (v/v), temperature- 30 °C, agitation speed- 200 rpm, and pH- 8.0. The bacterium was found to use an ortho-cleavage pathway for TPA degradation determined based on enzymatic and GC-MS studies. Moreover, during the degradation of TPA, the bacterium was observed to produce polyhydroxyalkanoate (PHA)-a biopolymer. Biodegradation of 120 mM TPA resulted in an accumulation of PHA. The PHA granules were visualized using fluorescence and transmission electron microscopy and were later characterized using FTIR spectroscopy. Furthermore, the robustness of the bacterium was demonstrated by its ability to degrade TPA in real industrial wastewater. Overall, R. erythropolis (MTCC 3951) hold the potential for controlling TPA pollution in the environment and vis-à-vis the production of PHA biopolymer.

Sustainable utilization of fruit and vegetable waste bioresources for bioplastics production

Nowadays, rapidly increasing production, use and disposable of plastic products has become one of the utmost environmental issues. Our current circumstances in which the food supply chain is demonstrated as containing plastic particles and other plastic-based impurities, represents a significant health risk to humans, animals, and environmental alike. According to this point of view, biodegradable plastic material aims to produce a more sustainable and greener world with a lower ecological impact. Bioplastics are being investigated as an environmentally friendly candidate to address this problem and hence global bioplastic production has seen significant growth and expansion in recent years. This article focuses on a few critical issues that must be addressed for bioplastic production to become commercially viable. Although the reduction of fruit and vegetable waste biomass has an apparent value in terms of environmental benefits and sustainability, commercial success at industrial scale has remained flat. This is due to various factors, including biomass feedstocks, pretreatment technologies, enzymatic hydrolysis, and scale-up issues in the industry, all of which contribute to high capital and operating costs. This review paper summarizes the global overview of bioplastics derived from fruit and vegetable waste biomass. Furthermore, economic and technical challenges associated with industrialization and diverse applications of bioplastics in biomedical, agricultural, and food-packaging fields due to their excellent biocompatibility properties are reviewed.HighlightsReview of the diverse types and characteristics of sustainability of biobased plasticsImproved pretreatment technologies can develop to enhance greater yieldEnzyme hydrolysis process used for bioplastic extraction & hasten industrial scale-upFocus on technical challenges facing commercialized the bioplasticsDetailed discussion on the application for sustainability of biodegradable plastics.

Valorization of organic wastes using bioreactors for polyhydroxyalkanoate production: Recent advancement, sustainable approaches, challenges, and future perspectives

Microbial polyhydroxyalkanoates (PHA) are encouraging biodegradable polymers, which may ease the environmental problems caused by petroleum-derived plastics. However, there is a growing waste removal problem and the high price of pure feedstocks for PHA biosynthesis. This has directed to the forthcoming requirement to upgrade waste streams from various industries as feedstocks for PHA production. This review covers the state-of-the-art progress in utilizing low-cost carbon substrates, effective upstream and downstream processes, and waste stream recycling to sustain entire process circularity. This review also enlightens the use of various batch, fed-batch, continuous, and semi-continuous bioreactor systems with flexible results to enhance the productivity and simultaneously cost reduction. The life-cycle and techno-economic analyses, advanced tools and strategies for microbial PHA biosynthesis, and numerous factors affecting PHA commercialization were also covered. The review includes the ongoing and upcoming strategies viz. metabolic engineering, synthetic biology, morphology engineering, and automation to expand PHA diversity, diminish production costs, and improve PHA production with an objective of "zero-waste" and "circular bioeconomy" for a sustainable future.

Valorisation of Pineapple Cannery Waste as a Cost Effective Carbon Source for Poly 3-hydroxyabutyrate (P3HB) Production

Pineapple is one of the most important agro-industrial sugar-based fruits in Thailand. In this study, the waste stream from pineapple cannery processing was utilised and evaluated for potential use in the production of a main biopolymer group widely known as polyhydroxyalkanoates (PHAs) through aerobic batch fermentation. Firstly, pineapple cannery waste (PCW) collected from three processing sources, pineapple juice (PAJ), peel and core juice (PCJ), and pulp-washing water (PWW), was used as a carbon source. Secondly, it was characterised and pretreated. Then, batch fermentation was performed by using the optimal condition (200 rpm agitation rate, 37 °C, and fermentation time of 72 h) under two different nutrient conditions in each type of carbon source. The results revealed that PHAs were produced during 24-72 h of fermentation without any interference. The PHAs product obtained was characterised by their properties. Interestingly, GC-MS showed homopolymer of poly 3-hydroxybutyrate (P3HB) group characteristics, such as OH, CH, and C=O; meanwhile, H1 NMR analysis showed signals corresponding to CH3, CH2, and CH, respectively. Remarkably, utilising the PCW showed a high-potential cheap carbon source for the production of PHAs as well as for the treatment of wastewater from the fruit industry.

Recent updates to microbial production and recovery of polyhydroxyalkanoates

The increasing use of synthetic polymers and their disposal has raised concern due to their adverse effects on the environment. Thus, other sustainable alternatives to synthetic plastics have been sought, such as polyhydroxyalkanoates (PHAs), which are promising microbial polyesters, mainly due to their compostable nature, biocompatibility, thermostability, and resilience, making this biopolymer acceptable in several applications in the global market. The large-scale production of PHAs by microorganisms is still limited by the high cost of production compared to conventional plastics. This review reports some strategies mentioned in the literature aimed at production and recovery, paving the way for the bio-based economy. For this, some aspects of PHAs are addressed, such as synthesis, production systems, process control using by-products from industries, and advances and challenges in the downstream. The bioplastics properties made them a prime candidate for food, pharmaceutical, and chemical industrial applications. With this paper, it is possible to see that biodegradable polymers are promising materials, mainly for reducing the pollution produced by polymers derived from petroleum.

Pineapple waste in animal feed: A review of nutritional potential, impact and prospects

Pineapple is a commodity and economic fruit with a high market potential worldwide. Almost 60 % of the fresh pineapple, such as peels, pulp, crowns and leaves, are agricultural waste. It is noteworthy that the waste has a high concentration of crude fibre, proteins, ascorbic acid, sugars and moisture content. The pineapple waste utilisation in animal feed has recently drawn the attention of many investigators to enhance growth performance and concomitantly reduce environmental pollution. Its inclusion in animal feed varies according to the livestock, such as feed block, pelleted or directly used as a roughage source for ruminants. The pineapple waste is also fermented to enrich the nutrient content of poultry feed. To date, the inclusion of pineapple waste in animal feed is optimistic only not for livestock but also for farmed fish. Indeed, it is an ideal strategy to improve the feed supply to the farm. This paper aims to overview the source, nutritional composition, and application of pineapple waste in animal feed. The recent findings on its effect on animal growth performance, nutrition and disease control are discussed comprehensively and summarised. The review also covers its benefits, potential impacts on sustainable farming and future perspectives.

Biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxvalerate) from volatile fatty acids by Cupriavidus necator

A promising strategy to alleviate the plastic pollution from traditional petroleum-based plastics is the application of biodegradable plastics, in which polyhydroxyalkanoates (PHAs) have received increasing interest owing to their considerable biodegradability. In the PHAs family, poly(3-hydroxybutyrate-co-3-hydroxvalerate) (PHBV) has better mechanical properties, which possesses broader application prospects. With this purpose, the present study adopted Cupriavidus necator to synthesize PHBV utilizing volatile fatty acids (VFAs) as sole carbon sources. Results showed that the concentration and composition of VFAs significantly influenced the production of PHAs. Especially, even carbon VFAs (acetate and butyrate) synthesized only poly(3-hydroxybutyrate) (PHB), while the addition of odd carbon VFAs (propionate and valerate) resulted in PHBV production. The 3-hydroxyvalerate (3HV) contents in PHBV were directly determined by the specific VFAs compositions, in which valerate was the preferred substrate for 3HV accumulation. After optimization by response surface methodology, the highest PHBV accumulation achieved 79.47% in dry cells, and the conversion efficiency of VFAs to PHBV reached 40%, with the PHBV production of 1.20 ± 0.05 g/L. This study revealed the metabolic rule of VFAs converting into PHAs by C. necator and figured out the optimal VFAs condition for PHBV accumulation, which provides a valuable reference for developing downstream strategies of PHBV production in industrial applications in future.

The earth-star basidiomycetous mushroom Astraeus odoratus produces polyhydroxyalkanoates during cultivation on malt extract

Polyhydroxyalkanoates (PHAs) including poly-3-hydroxybutyrate (P3HB) as secondary metabolisms were in vitro produced by the edible basidiomycetous mushroom Astraeus odoratus during its growth on malt agar extract. Various carbon and nitrogen sources containing cellulose, glucose, glycerol, rice straw powder, soybean meal and peptone were investigated for the growth of basidiomycetous mushrooms. During cultivation, the A. odoratus culture exudated the considerably extracellular fluid up to approx. 2.3 ml on 2% malt extract agar plate within 7 days. The chemical compounds of the exudated fluid were further investigated by Fourier-transform infrared spectroscopy (FTIR) and gas chromatography/mass spectrometry (GC/MS); and its morphology of the lyophilized sample was observed by scanning electron microscope (SEM). FTIR results showed the characteristic bands of OH at 3445 cm^-1, CH/CH₂/symmetric CH₃ (stretch) at 2923 and 2852 cm^-1, C=O at 1730 cm^-1, asymmetric CH₃ (bend) at 1454 and 1414 cm^-1, C-O of COO- at 1396 cm^-1 and C-O-C at 1223, 1160, 1116, 1058 and 1019 cm^-1 which were similar to the absorptive characteristics of P3HB. Methyl ester derivatives of GC/MS results identified 7 compounds including: 3-hydroxybutanoic (monomer of PHB), aminobenzoic, salicylic, hexadecenoic, octadecadienoic, octadecenoic and octadecanoic acids. SEM images revealed a fibriform and porous materials. Hence, the occurrence of PHAs was first described in a basidiomycetous mushroom A. odoratus. Thus, PHAs could be found not only in bacteria and but also in basidiomycetous mushroom, which can be promising target for bioplastics and green environmental studies.

Valorization of fruit wastes for circular bioeconomy: Current advances, challenges, and opportunities

The demands for fruits and processed products have significantly increased following the surging human population growth and rising health awareness. However, an enormous amount of fruit waste is generated during their production life-cycle due to the inedible portion and perishable nature, which become a considerable burden to the environment. Embracing the concept of "circular economy", these fruit wastes represent sustainable and renewable resources and can be integrated into biorefinery platforms for valorization into a wide range of high-value products. To fully realize the potential of fruit waste in circular bioeconomy and provide insights on future commercial-scale applications, this review presented the recycling and utilization of fruit wastes in various applications, particularly focusing on pollutant bioremediation, renewable energy and biofuel production, biosynthesis of bioactive compounds and low-cost microbial growth media. Furthermore, the challenges of efficient valorization of fruit wastes were discussed and future prospects were proposed.

Myco-biorefinery approaches for food waste valorization: Present status and future prospects

Increases in population and urbanization leads to generation of a large amount of food waste (FW) and its effective waste management is a major concern. But putrescible nature and high moisture content is a major limiting factor for cost effective FW valorization. Bioconversion of FW for the production of value added products is an eco-friendly and economically viable strategy for addressing these issues. Targeting on production of multiple products will solve these issues to greater extent. This article provides an overview of bioconversion of FW to different value added products.

Microbial biotechnology approaches for conversion of pineapple waste in to emerging source of healthy food for sustainable environment

One of the most significant and difficult jobs in food sustainability, is to make use of waste in the vegetable and fruit processing sectors. The discarded fruits along with their waste materials, is anticipated to have potential use for further industrial purposes via extraction of functional ingredients, extraction of bioactive components, fermentation. As a result of its abundant availability, simplicity and safe handling, and biodegradability, pineapple waste is now the subject of extensive research. It is regarded as a resource for economic development. This vast agro-industrial waste is being investigated as a low-cost raw material to produce a variety of high-value-added goods. Researchers have concentrated on the exploitation of pineapple waste, particularly for the extraction of prebiotic oligosaccharides as well as bromelain enzyme, and as a low-cost source of fibre, biogas, organic acids, phenolic antioxidants, and ethanol. Thus, this review emphasizes on pineapple waste valorisation approaches, extraction of bioactive and functional ingredients together with the advantages of pineapple waste to be used in many areas. From the socioeconomic perspective, pineapple waste can be a new raw material source to the industries and may potentially replace the current expensive and non-renewable sources. This review summarizes various approaches used for pineapple waste processing along with several important value-added products gained which could contribute towards healthy food and a sustainable environment.

Polyhydroxybutyrate (PHB) produced from red grape pomace: Effect of purification processes on structural, thermal and antioxidant properties

Red grape pomace was used as a source for poly(3-hydroxybutyrate) (PHB) production, which was then subject to a range of purification processes. The different PHB biopolymers were characterized for chemical structure, crystallinity, thermal properties, colour, release of compounds into different food simulants and antioxidant inhibition, and comparisons were made with a commercially available PHB. An increase in purification steps did not have a significant effect on the high thermal stability of the extracted biopolymer, but it decreased the degree of crystallinity and the presence of amino acids and aromatic compounds. With additional purification, the PHB powders also whitened and the number of components released from the biopolymer into food simulants decreased. The released compounds presented antioxidant inhibition, which has not been previously reported in the literature or with commercially available polyhydroxyalkanoates. This is of great interest for food packaging and biomedical industries where the addition of antioxidant additives to improve PHB functional properties may not be necessary and could be avoided.

Processing Agroindustry By-Products for Obtaining Value-Added Products and Reducing Environmental Impact

Over four billion tons of foods are produced annually on the planet, and about a third is wasted. A minimal part of this waste is incinerated or sent to landfills for treatment, avoiding contamination and diseases; the rest is disposed of elsewhere. The current review was aimed at broadening the panorama on the potential of agroindustrial by-products in applications such as biofuels, biomaterials, biocompounds, pharmaceuticals, and food ingredients. It also exposes the main chemical, physical, and biochemical treatments for converting by-products into raw materials with added value through low environmental impact processes. The value of agroindustrial waste is limited due to the scarce information available. There is a need for further research in unexplored areas to find ways of adding value to these by-products and minimizing their contamination. Instead of throwing away or burning by-products, they can be transformed into useful materials such as polymers, fuels, antioxidants, phenols, and lipids, which will effectively reduce food waste and environmental impact.

A review on polyhydroxyalkanoate production from agricultural waste Biomass: Development, Advances, circular Approach, and challenges

Polyhydroxyalkanoates are biopolymers produced by microbial fermentation. They have excellent biodegradability and biocompatibility, which are regarded as promising substitutes for traditional plastics in various production and application fields. This review details the research progress in PHA production from lignocellulosic crop residues, lipid-type agricultural wastes, and other agro-industrial wastes such as molasses and whey. The effective use of agricultural waste can further reduce the cost of PHA production while avoiding competition between industrial production and food. The latest information on fermentation parameter optimization, fermentation strategies, kinetic studies, and circular approach has also been discussed. This review aims to analyze the crucial process of the PHA production from agricultural wastes to provide support and reference for further scale-up and industrial production.

Harnessing fruit waste for poly-3-hydroxybutyrate production: A review

Poly-3-hydroxybutyrate is a biopolymer which has shown tremendous potential for replacing conventional petroleum-based plastics for plummeting the plastic pollution problem. However, the production cost of PHB is high which makes it less attractive for commercial use. To tackle this challenge, various researchers suggest the search for low-cost substrates and energy efficient technologies for PHB production. In this regard, the waste generated from fruit processing industries or fruit wastes could be pre-processed and fermented for effectively generating PHB. Therefore, the aim of this review was to focus on the methods of fruit waste pre-processing and the effect of fermentation variables on PHB production using fruit waste as a substrate. The relevant research findings on the use of different microorganisms, PHB production conditions and fruit waste-based substrates are also covered. Analysis of various studies revealed that pineapple and mixed fruit waste are effective for PHB production.

Opportunities for the Use of Brazilian Biomass to Produce Renewable Chemicals and Materials

This Review highlights the principal crops of Brazil and how their harvest waste can be used in the chemicals and materials industries. The Review covers various plants; with grains, fruits, trees and nuts all being discussed. Native and adopted plants are included and studies on using these plants as a source of chemicals and materials for industrial applications, polymer synthesis, medicinal use and in chemical research are discussed. The main aim of the Review is to highlight the principal Brazilian agricultural resources; such as sugarcane, oranges and soybean, as well as secondary resources, such as andiroba brazil nut, buriti and others, which should be explored further for scientific and technological applications. Furthermore, vegetable oils, carbohydrates (starch, cellulose, hemicellulose, lignocellulose and pectin), flavones and essential oils are described as well as their potential applications.

Polyhydroxyalkanoate and its efficient production: an eco-friendly approach towards development

Polyhydroxyalkanoate (PHA) is the most promising solution to major ecological problem of plastic accumulation. The biodegradable and biocompatible properties of PHA make it highly demanding in the biomedical and agricultural field. The limited market share of PHA industries despite having tremendous demand as concerned with environment has led to knock the doors of scientific research for finding ways for the economic production of PHA. Therefore, new methods of its production have been applied such as using a wide variety of feedstock like organic wastes and modifying PHA synthesizing enzyme at molecular level. Modifying metabolic pathways for PHA production using new emerging techniques like CRISPR/Cas9 technology has simplified the process spending less amount of time. Using green solvents under pressurized conditions, ionic liquids, supercritical solvents, hypotonic cell disintegration for release of PHA granules, switchable anionic surfactants and even digestion of non-PHA biomass by animals are some novel strategies for PHA recovery which play an important role in sustainable production of PHA. Hence, this review provides a view of recent applications, significance of PHA and new methods used for its production which are missing in the available literature.

Production of Sustainable and Biodegradable Polymers from Agricultural Waste

Agro-wastes are derived from diverse sources including grape pomace, tomato pomace, pineapple, orange, and lemon peels, sugarcane bagasse, rice husks, wheat straw, and palm oil fibers, among other affordable and commonly available materials. The carbon-rich precursors are used in the production bio-based polymers through microbial, biopolymer blending, and chemical methods. The Food and Agriculture Organization (FAO) estimates that 20–30% of fruits and vegetables are discarded as waste during post-harvest handling. The development of bio-based polymers is essential, considering the scale of global environmental pollution that is directly linked to the production of synthetic plastics such as polypropylene (PP) and polyethylene (PET). Globally, 400 million tons of synthetic plastics are produced each year, and less than 9% are recycled. The optical, mechanical, and chemical properties such as ultraviolet (UV) absorbance, tensile strength, and water permeability are influenced by the synthetic route. The production of bio-based polymers from renewable sources and microbial synthesis are scalable, facile, and pose a minimal impact on the environment compared to chemical synthesis methods that rely on alkali and acid treatment or co-polymer blending. Despite the development of advanced synthetic methods and the application of biofilms in smart/intelligent food packaging, construction, exclusion nets, and medicine, commercial production is limited by cost, the economics of production, useful life, and biodegradation concerns, and the availability of adequate agro-wastes. New and cost-effective production techniques are critical to facilitate the commercial production of bio-based polymers and the replacement of synthetic polymers.

Formulation of a fermentation substrate from pineapple and sacha inchi wastes to grow Weissella cibaria

Gold honey variety pineapple wastes and sacha inchi sub-products (SIS) were characterized in their elemental, physical, and chemical form in order to formulate a supplemented fermentation substrate (SFS) for the growth Weissella cibaria. The peels and fresh cores of the pineapple (FPP, FPC) were dried and ground (PPP, PPC) and then mixed (MCPP). The following procedures were then undertaken: a physicochemical characterization (moisture, a_w, pH, acidity, and soluble solids) of the SIS, FPP, FPC, PPP, and PPC; a proximal characterization of he FPP, FPC, SIS, and SFS; and an elemental analysis (C-N₂-H₂-O₂-S) of the MCPP, SIS, and W. cibaria, which allowed the stoichiometric equation to be defined and the SFS to be formulated. We then evaluated the effect that homogenization and heating to boiling point had on the concentration of reducing sugars in the SFS (g L^-1). Finally, W. cibaria´s kinetic fermentation parameters were evaluated in the SFS and in a commercial substrate (control). The results showed FPP and FPC yields of 26.02 ± 0.58 and 14.69 ± 1.13%, respectively; a higher total sugar content in FPC (7.21%) than in FPP (6.65%); a high crude protein content in SIS (56.70%), and a C:N₂ ratio of 6.50:1.00. Moreover, the highest concentration of reducing sugars (4.44 ± 0.29 g L^-1) in the SFS was obtained with 5 h of hydrolysis under homogenization pre-treatments and heating until boiling. The SFS allowed the adaptation of W. cibaria, and there was a biomass production of 2.93 g L^-1 and a viability of 9.88 log CFU mL^-1. The formulation of an unconventional fermentation substrate from -Agro-industrial wastes of pineapple and sacha inchi to produce valuable products (such as lactic acid biomass through fermentation), is an excellent perspective for large-scale application.

Recent advances in polyhydroxyalkanoate production: Feedstocks, strains and process developments

Polyhydroxyalkanoates (PHAs) have been actively studied in academia and industry for their properties comparable to petroleum-derived plastics and high biocompatibility. However, the major limitation for commercialization is their high cost. Feedstock costs, especially carbon costs, account for the majority of the final cost. Finding cheap feedstocks for PHA production and associated process development are critical for a cost-effective PHA production. In this study, waste materials from different sources, particularly lignocellulosic biomass, were proposed as suitable feedstocks for PHA production. Strains involved in the conversion of these feedstocks into PHA were reviewed. Newly isolated strains were emphasized. Related process development, including the factors that affect PHA production, fermentation modes and downstream processing, was elaborated upon.

Response surface method for polyhydroxybutyrate (PHB) bioplastic accumulation in Bacillus drentensis BP17 using pineapple peel

Polyhydroxybutyrate (PHB) is a biodegradable biopolymer which is useful for various applications including packing, medical and coating materials. An endospore-forming bacterium (strain BP17) was isolated from composted soil and evaluated for PHB production. Strain BP17, taxonomically identified as Bacillus drentensis, showed enhanced PHB accumulation and was selected for further studies. To achieve maximum PHB production, the culture conditions for B. drentensis BP17 were optimized through response surface methodology (RSM) employing central composite rotatable design (CCRD). The final optimum fermentation conditions included: pineapple peel solution, 11.5% (v/v); tryptic soy broth (TSB), 60 g/L; pH, 6.0; inoculum size, 10% (v/v) and temperature, 28°C for 36 h. This optimization yielded 5.55 g/L of PHB compared to the non-optimized condition (0.17 g/L). PHB accumulated by B. drentensis BP17 had a polydispersity value of 1.59 and an average molecular weight of 1.15x105 Da. Thermal analyses revealed that PHB existed as a thermally stable semi-crystalline polymer, exhibiting a thermal degradation temperature of 228°C, a melting temperature of 172°C and an apparent melting enthalpy of fusion of 83.69 J/g. It is evident that B. drentensis strain BP17 is a promising bacterium candidate for PHB production using agricultural waste, such as pineapple peel as a low-cost alternative carbon source for PHB production.

RSM-GA Based Optimization of Bacterial PHA Production and In Silico Modulation of Citrate Synthase for Enhancing PHA Production

The inexhaustible nature and biodegradability of bioplastics like polyhydroxyalkanoates (PHAs) make them suitable assets to replace synthetic plastics. The eventual fate of these eco-friendly and non-toxic bioplastics relies upon the endeavors towards satisfying cost and, in addition, execution necessity. In this study, we utilized and statistically optimized different food (kitchen-/agro-) waste as a sole carbon/nitrogen source for the production of PHA at a reduced cost, indicating a proficient waste administration procedure. Seven different types of kitchen-/agro-waste were used as unique carbon source and four different types of nitrogen source were used to study their impact on PHA production by Bacillus subtilis MTCC 144. Among four different studied production media, mineral salt medium (MSM) (biomass: 37.7 g/L; cell dry weight: 1.8 g/L; and PHA: 1.54 g/L) was found most suitable for PHA production. Further, carbon and nitrogen components of MSM were optimized using one-factor-at-a-time experiments, and found that watermelon rind (PHA = 12.97 g/L) and pulse peel (PHA = 13.5 g/L) were the most suitable carbon and nitrogen sources, respectively, in terms of PHA (78.60%) recovery. The concentrations of these factors (sources) were statistically optimized using response surface methodology coupled with the genetic algorithm approach. Additionally, in order to enhance microbial PHA production, the interaction of citrate synthase, a key enzyme in the TCA cycle, with different known inhibitors was studied using in silico molecular docking approach. The inhibition of citrate synthase induces the blockage of the tricarboxylic cycle (TCA), thereby increasing the concentration of acetyl-CoA that helps in enhanced PHA production. Molecular docking of citrate synthase with different inhibitors of PubChem database revealed that hesperidin (PubChem compound CID ID 10621), generally present in citrus fruits, is the most efficient inhibitor of the TCA cycle with the binding score of –11.4 and warrants experimental validation. Overall, this study provides an efficient food waste management approach by reducing the production cost and enhancing the production of PHA, thereby lessening our reliance on petroleum-based plastics.

Production of bioplastic through food waste valorization

The tremendous amount of food waste from diverse sources is an environmental burden if disposed of inappropriately. Thus, implementation of a biorefinery platform for food waste is an ideal option to pursue (e.g., production of value-added products while reducing the volume of waste). The adoption of such a process is expected to reduce the production cost of biodegradable plastics (e.g., compared to conventional routes of production using overpriced pure substrates (e.g., glucose)). This review focuses on current technologies for the production of polyhydroxyalkanoates (PHA) from food waste. Technical details were also described to offer clear insights into diverse pretreatments for preparation of raw materials for the actual production of bioplastic (from food wastes). In this respect, particular attention was paid to fermentation technologies based on pure and mixed cultures. A clear description on the chemical modification of starch, cellulose, chitin, and caprolactone is also provided with a number of case studies (covering PHA-based products) along with a discussion on the prospects of food waste valorization approaches and their economic/technical viability.