Use of residual banana for polyhydroxybutyrate (PHB) production: case of study in an integrated biorefinery

Isolation of Massilia species capable of degrading Poly(3-hydroxybutyrate) isolated from eggplant (Solanum melongena L.) field

Poly(3-hydroxybutyrate) (PHB) is crucial for replacing petroleum-based plastics, an essential step towards fostering a bio-based economy. This shift is urgently needed to safeguard human health and preserve natural ecosystems. PHB is one of the most extremely commercialized bio-plastics. Although. significant progress has been made in identifying bacteria that produce PHB, fewer bacteria capable of degrading it have been discovered. Four newly isolated Massilia strains capable of degrading PHB were discovered in eggplant (Solanum melongena L.) field soil. Their PHB-degrading abilities were investigated under different temperatures and media using emulsified solid-media based cultures. The strains belong to the genus Massilia, were evaluated for their effectiveness. Among them, Massilia sp. JJY02, was selected for its exceptional PHB degradation. PHB degradation was confirmed by monitoring changes in the physical and chemical properties of PHB films using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). After 20 days of cultivation with PHB film, Massilia sp. JJY02 achieved approximately 90% PHB degradation at 28 °C. All the novel strains were capable of producing carotenoid-type pigments and indole-acetic acid (IAA). Among them, Massilia sp. JJY03 and JJY04 showed phosphate solubilization activity. This study demonstrated that soil bacteria from eggplant have both PHB-degrading and plant growth promoting capabilities, marking the first instance of showing that species of Massilia can degrade PHB.

Integral multi-valorization of agro-industrial wastes: A review

Agriculture and industries related to the agriculture sector generate a large amount of waste each year. These wastes are usually burned or dumped, causing damage to the environment, the economy and society. Due to their composition, they have great potential for obtaining high value-added products in biorefineries. This fact, added to the growing demand for energy and chemicals from fossil resources, is driving the interest of the scientific community in them. Biorefinery processes are hardly profitable when applied individually, so a better alternative is to develop integrated multi-feedstock and multi-product biorefinery schemes using all biomass fractions in a zero-waste approach. However, for industrial scale application, extensive research, scale-up studies, and techno-economic and environmental feasibility analyses are needed. This review compiles information on integrated multi-biorefinery processes from agro-industrial wastes to shed light on the path towards sustainable development and circular bioeconomy.

Taguchi approach for assessing supercritical CO2 (sCO2) fluid extraction of polyhydroxyalkanoate (PHA) from Chlorella Vulgaris sp. microalgae

This research explicitly investigates the utilization of Chlorella Vulgaris sp. microalgae as a renewable source for lipid production, focusing on its application in bioplastic manufacturing. This study employed the supercritical fluid extraction technique employing supercritical CO2 (sCO2) as a green technology to selectively extract and produce PHA's precursor utilizing CO2 solvent as a cleaner solvent compared to conventional extraction method. The study assessed the effects of three extraction parameters, namely temperature (40-60 °C), pressure (15-35 MPa), and solvent flow rate (4-8 ml/min). The pressure, flowrate, and temperature were found to be the most significant parameters affecting the sCO2 extraction. Through Taguchi optimization, the optimal parameters were determined as 60 °C, 35 MPa, and 4 ml/min with the highest lipid yield of 46.74 wt%; above-average findings were reported. Furthermore, the pretreatment process involved significant effects such as crumpled and exhaustive structure, facilitating the efficient extraction of total lipids from the microalgae matrix. This study investigated the microstructure of microalgae biomatrix before and after extraction using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Fourier-transform infrared spectroscopy (FTIR) was utilized to assess the potential of the extracted material as a precursor for biodegradable plastic production, with a focus on reduced heavy metal content through inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis. The lipid extracted from Chlorella Vulgaris sp. microalgae was analysed using gas chromatography-mass spectrometry (GC-MS), identifying key constituents, including oleic acid (C18H34O2), n-Hexadecanoic acid (C16H32O2), and octadecanoic acid (C18H36O2), essential for polyhydroxyalkanoate (PHA) formation.

Bioplastic (poly-3-hydroxybutyrate)-producing Massilia endophytica sp. nov., isolated from Cannabis sativa L. 'Cheungsam'

A rod-shaped, motile, Gram-negative bacterial strain named DM-R-R2A-13T was isolated from the plant Cannabis sativa L. 'Cheungsam'. The phylogenetic analysis of the 16S rRNA gene sequence revealed that strain DM-R-R2A-13T belongs to the family Oxalobacteraceae and is closely related to members of the genus Massilia, with Massilia flava (97.58% sequence similarity) and Massilia armeniaca (97.37% sequence similarity) being the closest members. The digital DNA-DNA hybridization (dDDH) values between strain DM-R-R2A-13T and Massilia flava CGMCC 1.10685T and Massilia armeniaca ZMN-3Twere 22.2% and 23.3%, while the average nucleotide identity (ANI) values were 78.85% and 79.63%, respectively. The DNA G+C content was measured to be 64.6 mol%. Moreover, the bacterium was found to contain polyhydroxyalkanoate (PHA) granules based on transmission electron microscopy, indicating its potential to produce bioplastic. Genome annotation revealed the presence of PHA synthase genes (phaC, phaR, phaP, and phaZ), and the biopolymer was identified as poly-3-hydroxybutyrate (PHB) based on nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR) analyses. Using maltose as a carbon source, the strain produced PHB of up to 58.06% of its dry cell weight. Based on the phenotypic, chemotaxonomic, and phylogenetic characteristics, it has been determined that DM-R-R2A-13T represents a novel species belonging to the genus Massilia. As such, the name Massilia endophytica sp. nov. is proposed for this newly identified species. The type strain is DM-R-R2A-13T (= KCTC 92072T = GDMCC 1.2920T).

Life-cycle assessment of yeast-based single-cell protein production with oat processing side-stream

Production of fish meal and plant-based feed proteins continues to increase to meet the growing demand for seafood, leading to impacts on marine and terrestrial ecosystems. Microbial proteins such as single-cell proteins (SCPs) have been introduced as feed alternatives since they can replace current fish feed ingredients, e.g., soybean, which are associated with negative environmental impacts. Microbial protein production also enables utilization of grain processing side-streams as feedstock sources. This study assesses the environmental impacts of yeast-based SCP using oat side-stream as feedstock (OS-SCP). Life-cycle assessment with a cradle-to-gate approach was used to quantify global warming, freshwater eutrophication, marine eutrophication, terrestrial acidification, land use, and water consumption of OS-SCP production in Finland. Dried and wet side-streams of oat were compared with each other to identify differences in energy consumption and transportation effects. Sensitivity analysis was performed to examine the difference in impacts at various locations and fermentation times. Benchmarking was used to evaluate the environmental impacts of OS-SCP and other feed products, including both conventional and novel protein products. Results highlight the importance of energy sources in quantifying the environmental performance of OS-SCP production. OS-SCP produced with dried side-streams resulted in higher global warming (16.3 %) and water consumption (7.5 %) than OS-SCP produced from wet side-streams, reflecting the energy and water requirements for the drying process. Compared with conventional products, such as soy protein concentrates, OS-SCP resulted in 61 % less land use, while exacerbating the environmental impacts in all the other categories. OS-SCP had more impact on global warming (205-754 %), water consumption (166-1401 %), freshwater eutrophication (118-333 %), and terrestrial acidification (85-340 %) than other novel products, including yeast protein concentrate, methanotrophic bacterial SCP, and insect meal, while lowering global warming (11 %) and freshwater eutrophication (20 %) compared with dry microalgae biomass.

Polyhydroxyalkanoate Production from Fruit and Vegetable Waste Processing

Traditional plastics represent a tremendous threat to the environment because of increases in polluting manufacturing as well as their very extended degradation time. Polyhydroxyalkanoates (PHAs) are polymers with similar performance to plastic but are compostable and synthesizable from renewable sources and therefore could be a replacement for fossil-based plastics. However, their production costs are still too high, thus demanding the investigation of new and cheap substrates. In this sense, agricultural wastes are attractive because they are inexpensive and largely available. Specifically, fruit and vegetables are rich in sugars that could be fermented into PHAs. In this work two strains, Cupriavidus necator DSM 545 and Hydrogenophaga pseudoflava DSM 1034, well-known PHA-producing microbes, were screened for their ability to grow and accumulate PHAs. Ten different fruit and vegetable processing waste streams, never before reported in combination with these strains, were tested. Residues from red apple and melon were found to be the most suitable feedstocks for PHA production. Under specific selected conditions, C. necator DSM 545 accumulated up to 7.4 and 4.3 g/L of 3-hydroxybutyrate (3HB) from red apple and melon, respectively. Copolymer production was also obtained from melon. These results confirm the attractiveness of food processing waste as a promising candidate for PHA production. Ultimately, these novel substrates draw attention for future studies on process optimization and upscaling with C. necator.

From Biorefinery to Food Product Design: Peach (Prunus persica) By-Products Deserve Attention

There is an increasing demand for functional foods to attend the consumers preference for products with health benefits. Peach (Prunus persica), from Rosaceae family, is a worldwide well-known fruit, and its processing generates large amounts of by-products, consisting of peel, stone (seed shell + seed), and pomace, which represent about 10% of the annual global production, an equivalent of 2.4 million tons. Some studies have already evaluated the bioactive compounds from peach by-products, although, the few available reviews do not consider peach by-products as valuable materials for product design methodology. Thereby, a novelty of this review is related to the use of these mostly unexplored by-products as alternative sources of valuable components, encouraging the circular bioeconomy approach by designing new food products. Besides, this review presents recent peach production data, compiles briefly the extraction methods for the recovery of lipids, proteins, phenolics, and fiber from peach by-products, and also shows in vivo study reports on anti-inflammatory, anti-obesity, and anti-cerebral ischemia activities associated with peach components and by-product. Therefore, different proposals to recover bioactive fractions from peach by-products are provided, for further studies on food-product design.

Study on the production of high 3HV content PHBV via an open fermentation with waste silkworm excrement as the carbon source by the haloarchaeon Haloferax mediterranei

Silkworm excrement is hard to be degraded or bio-utilized by environmental microorganisms due to its high content of heavy metals and antimicrobial biomacromolecules in mulberry leaves. In traditional Chinese silk industry, the silkworm excrement results in environmental problems. In this study, the silkworm excrement after chlorophyll ethanol-extraction was researched. An open fermentation strategy was developed using the silkworm excrement as the sole or partial carbon source by haloarchaea to accumulate polyhydroxyalkanoates. As a haloarchaeon with strong carbon source utilization ability, Haloferax mediterranei was found to accumulate a certain amount of poly(3-hydroxybutyrate-co-3-hydroxyvalerate; PHBV) using waste silkworm excrement. The results showed that the addition of silkworm excrement into glucose based fermentation medium can significantly improve the production of PHBV. Using a mixture carbon source including the extract of silkworm excrement and glucose (with a 1:1 carbon content ratio), the yield of PHBV was 1.73 ± 0.12 g/l, which showed a 26% increase than that of fermentation without the silkworm excrement addition. When the NaCl content of medium was set to approximately 15%, fermentation without sterilization was performed using silkworm excrement as the carbon source. Moreover, the addition of the silkworm excrement extract could increase the 3-hydroxyvalerate (3 HV) content of PHBV regardless of the sterilization or non-sterilization fermentation conditions. When using silkworm excrement as the sole carbon source, the 3 HV content was as high as 16.37 ± 0.54 mol %. The real-time quantitative PCR results showed that the addition of the silkworm excrement could specifically enhance the expression of genes involved in the aspartate/2-ketobutyric acid pathway related to 3 HV synthesis in H. mediterranei, and further analysis of the amino acid of the silkworm excrement suggested that the high content of threonine in the silkworm excrement might be the reason for the increase of 3 HV content. Taken together, the success of non-sterile fermentation in hypersaline condition using haloarchaea implied a novel way to reuse the silkworm excrement, which not only reduces the production costs of PHBV, but also is conducive to environmental protection.

Comparative Analysis the Complete Chloroplast Genomes of Nine Musa Species: Genomic Features, Comparative Analysis, and Phylogenetic Implications

Musa (family Musaceae) is monocotyledonous plants in order Zingiberales, which grows in tropical and subtropical regions. It is one of the most important tropical fruit trees in the world. Herein, we used next-generation sequencing technology to assemble and perform in-depth analysis of the chloroplast genome of nine new Musa plants for the first time, including genome structure, GC content, repeat structure, codon usage, nucleotide diversity and etc. The entire length of the Musa chloroplast genome ranged from 167,975 to 172,653 bp, including 113 distinct genes comprising 79 protein-coding genes, 30 transfer RNA (tRNA) genes and four ribosomal RNA (rRNA) genes. In comparative analysis, we found that the contraction and expansion of the inverted repeat (IR) regions resulted in the doubling of the rps19 gene. The several non-coding sites (psbI-atpA, atpH-atpI, rpoB-petN, psbM-psbD, ndhf-rpl32, and ndhG-ndhI) and three genes (ycf1, ycf2, and accD) showed significant variation, indicating that they have the potential of molecular markers. Phylogenetic analysis based on the complete chloroplast genome and coding sequences of 77 protein-coding genes confirmed that Musa can be mainly divided into two groups. These genomic sequences provide molecular foundation for the development and utilization of Musa plants resources. This result may contribute to the understanding of the evolution pattern, phylogenetic relationships as well as classification of Musa plants.

Techno-economic assessment of a sustainable and cost-effective bioprocess for large scale production of polyhydroxybutyrate

The rapid depletion of crude-oil resource which sustains a conventional petroleum refinery together with its environmental impact has led to the search for more sustainable alternatives. In this context, biorefinery serves to fulfil the aim by utilizing waste resources. Hence, this study focused on techno-economic assessment of PHB production at large scale from waste carob pods in a closed-loop biorefinery setup. Firstly, the use of pure sugars in SC1 was shifted to use of carob pods as feedstock in SC2, upgradation of stirred tank bioreactor with novel annular gap bioreactor in SC3 and replacing the conventional centrifugation process with the upcoming ceramic membrane separation process in SC4. An Aspen plus™ flowsheet was developed by including the aforementioned novel strategies for PHB production. The effectiveness of PHB production under various scenarios was evaluated based on its pay-out period and turnover accumulated at the end of 7th year of a PHB plant operation. Instead of pure sugars as the feedstock (SC1), carob pod extract (SC2) reduced the pay-out period from 12.6 to 6.8 years. Likewise, switching onto ABR from the conventional STBR further decreased the pay-out period to 4.8 years. Finally, the use of ceramic membranes (SC4) instead of centrifugation resulted in a similar pay-out period of 4.8 years with increased turnover of about 1.4 billion USD. Thus, the use of carob pods along with an improved PHB titre in ABR and incorporation of affordable ceramic membrane technology for PHB rich biomass separation resulted in a highly cost-effective PHB production strategy.

Potencial de Biomasa en América del Sur para la Producción de Bioplásticos. Una Revisión

La biomasa es una fuente primaria renovable que ha generado mayor interés en el mundo durante los últimos años, debido a la oportunidad de obtener productos energéticos y no energéticos similares a los que se producen de las fuentes no renovables. En este sentido, América del Sur, por su ubicación geográfica, cuenta con alto potencial de generar y adicionar valor a la biomasa; por lo que esta investigación realiza una revisión descriptiva sobre la disponibilidad y potencial de biomasa en América del Sur, con el propósito de establecer los tipos y cantidad de bioplásticos biobasados y biodegradables (BBB) que se pueden producir en esta región. En primer lugar, se realizó una descripción de la biomasa, sus características y clasificación. Posterior a esto, se recopiló información de la biomasa generada en cada país, para finalmente describir los tipos de BBB existentes en la actualidad. La investigación reveló que en la región se pueden producir 204,42 millones de toneladas (MMt) de bioplástico basado en celulosa regenerada, 4,11 MMt de bioplástico basado en almidón, 0,58 MMt de ácido poliláctico y 8,68 MMt de polihidroxibutirato. Además, la producción de BBB es una alternativa que permite minimizar la contaminación ambiental producida por los plásticos sintéticos, ya que utiliza de manera eficiente y sostenible los residuos generados por actividades agropecuarias e industriales. Finalmente, este estudio permite ampliar el estado del arte e intensificar las ventajas que tienen los países de América del Sur con respecto a la generación de empleos y desarrollo industrial en zonas rurales.

Concomitant production of value-added products with polyhydroxyalkanoate (PHA) synthesis: A review

The concern over the damaging effects of petrochemical plastics has inspired innumerable researchers to synthesize green plastics. Polyhydroxyalkanoates (PHAs) are promising candidates as they are biodegradable and possess characteristics similar to conventional plastics. However, their large-scale production and market application still have a long way to go due to the high production cost associated. Approaches like using industrial wastes as substrates and developing green strategies for PHA extraction during downstream processing have been investigated to make the process more economical. Recently, PHA production cost was minimized by concomitant synthesis of other valuable bioproducts with PHA. Investigating these co-products and recovering them can also make the process circular bioeconomic. Therefore, the paper attempts to review the recent strategies for the simultaneous synthesis of value-added bioproducts with PHA together with the challenges and opportunities for their large-scale production and applications.

Evaluation of Fed-Batch Fermentation for Production of Polyhydroxybutyrate With a Banana Pulp Juice Substrate From an Agro Industrial By-Product

Pollution resulting from the persistence of plastics in the environment has driven the development of substitutes for these materials through fermentation processes using agro-industrial wastes. Polyhydroxybutyrate (PHB) is a rapidly biodegradable material with chemical and mechanical properties comparable to those of some petroleum-derived plastics. PHB accumulates intracellularly as an energy reserve in a wide variety of microorganisms exposed to nutritionally imbalanced media. The objective of this study was to evaluate the use of a banana waste product as a carbon source for PHB production. PHB was extracted by acid methanolysis and detected by gas chromatography-mass spectrometry. Eleven bacterial strains with potential for PHB production were evaluated by in vitro fermentation in a culture broth containing fructose as the carbon source and limited nitrogen. A 22 central composite rotational design was applied to optimize the concentrations of banana juice and ammonium chloride needed to maximize the PHB-producing biomass concentration. The process was then carried out in a 3 L fed-batch fermentation system that included an initial stage of biomass growth. Banana juice was used as the carbon source and fructose pulses were added to maintain the test sugar concentrations of 30, 40, and 50 g/L. The control strain, Cupriavidus necator (ATCC 17699), produced 2.816 g/L of PHB, while productivity of the most promising isolate, C. necator (CR-12), was 0.495 g/L. Maximum biomass production was obtained using 5% banana juice and 2 g/L ammonium chloride. PHB production was not detected in fed-batch fermentations supplemented with 30 or 40 g/L of fructose, while the mean PHB production in fermentations with 50 g/L of fructose was 1.3 g/L.

Persea Americana Agro-Industrial Waste Biorefinery for Sustainable High-Value-Added Products

Significant problems have arisen in recent years, such as global warming and hunger. These complications are related to the depletion and exploitation of natural resources, as well as environmental pollution. In this context, bioprocesses and biorefinery can be used to manage agro-industrial wastes for obtaining high-value-added products. A large number of by-products are composed of lignin and cellulose, having the potential to be exploited sustainably for chemical and biological conversion. The biorefinery of agro-industrial wastes has applications in many fields, such as pharmaceuticals, medicine, material engineering, and environmental remediation. A comprehensive approach has been developed toward the agro-industrial management of avocado (Persea americana) biomass waste, which can be transformed into high-value-added products to mitigate global warming, save non-renewable energy, and contribute to health and science. Therefore, this work presents a comprehensive review on avocado fruit waste biorefinery and its possible applications as biofuel, as drugs, as bioplastics, in the environmental field, and in emerging nanotechnological opportunities for economic and scientific growth.

Food waste valorization: Energy production using novel integrated systems

Management of food waste (FW) is a global challenge due to increasing population and economic activities. Presently, landfill and incineration are the keyways of FW management, while economical and environmental sustainability have been an issue. Therefore, the biological processes have been investigated for resource and energy recovery from FW. However, these biological approaches have certain drawbacks and cannot be a complete solution for FW management. Therefore, this review aims to offer a detailed and complete analysis of current available technologies to achieve environmental and economical sustainability. In this context, zero solid waste discharge for resource and energy recovery has been put into view. Corresponding to which several innovative technologies using integrated biological methods for resource and energy recovery from FW have been elucidated.

Sustainability of food waste biorefinery: A review on valorisation pathways, techno-economic constraints, and environmental assessment

The need to increase circularity of industrial systems to address limited resources availability and climate change has triggered the development of the food waste biorefinery concept. However, for the development of future sustainable industrial processes focused on the valorisation of food waste, critical aspects such as (i) the technical feasibility of the processes at industrial scale, (ii) the analysis of their techno-economic potential, including available quantities of waste, and (iii) a life cycle-based environmental assessment of benefits and burdens need to be considered. The goal of this review is to provide an overview of food waste valorisation pathways and to analyse to which extent these aspects have been considered in the literature. Although a plethora of food waste valorisation pathways exist, they are mainly developed at lab-scale. Further research is necessary to assess upscaled performance, feedstock security, and economic and environmental assessment of food waste valorisation processes.

Critical overview of biomass feedstocks as sustainable substrates for the production of polyhydroxybutyrate (PHB)

Polyhydroxybutyrates (PHBs) are a class of biopolymers produced by different microbial species and are biodegradable and biocompatible in nature as opposed to petrochemically derived plastics. PHBs have advanced applications in medical sector, packaging industries, nanotechnology and agriculture, among others. PHB is produced using various feedstocks such as glycerol, dairy wastes, agro-industrial wastes, food industry waste and sugars. Current focus on PHB research has been primarily on reducing the cost of production and, on downstream processing to isolate PHB from cells. Recent advancements to improve the productivity and quality of PHB include genetic modification of producer strain and modification of PHB by blending to develop desirable properties suited to diversified applications. Selection of feedstock plays a critical role in determining the economic feasibility and sustainability of the process. This review provides a bird's eye view of the suitability of different waste resources for producing polyhydroxybutyrate; providing state-of the art information and analysis.

Biorefinery of Biomass of Agro-Industrial Banana Waste to Obtain High-Value Biopolymers

On a worldwide scale, food demand is increasing as a consequence of global population growth. This makes companies push their food supply chains' limits with a consequent increase in generation of large amounts of untreated waste that are considered of no value to them. Biorefinery technologies offer a suitable alternative for obtaining high-value products by using unconventional raw materials, such as agro-industrial waste. Currently, most biorefineries aim to take advantage of specific residues (by either chemical, biotechnological, or physical treatments) provided by agro-industry in order to develop high-value products for either in-house use or for sale purposes. This article reviews the currently explored possibilities to apply biorefinery-known processes to banana agro-industrial waste in order to generate high-value products out of this residual biomass source. Firstly, the Central and Latin American context regarding biomass and banana residues is presented, followed by advantages of using banana residues as raw materials for the production of distinct biofuels, nanocellulose fibers, different bioplastics, and other high-value products Lastly, additional uses of banana biomass residues are presented, including energy generation and water treatment.

Recycling strategies for polyhydroxyalkanoate-based waste materials: An overview

The plastics market is dominated by fossil-based polymers, but their gradual replacement by bioplastics (e.g., polyhydroxyalkanoates) is occurring. However, recycling strategies need to be developed to truly unveil the impact of bioplastics on waste accumulation. This review provides a state of the art of recycling strategies investigated for polyhydroxyalkanoate-based polymers and proposes future research avenues. Research on mechanical and chemical recycling is dominated by the use of extrusion and pyrolysis, respectively, while that on biodegradation of polyhydroxyalkanoates is related to soil and aquatic samples, and to anaerobic digestion towards biogas production. Research gaps exist in the relationships between polymer composition and ease of use of all recycling strategies investigated. This is of utmost importance since it will influence the need for separation at the source. Therefore, research emphasis needs to be given to the area to follow the continuous improvement of the process economics towards widespread commercial production of polyhydroxyalkanoates.

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.

Integral use of plants and their residues: the case of cocoyam (Xanthosoma sagittifolium) conversion through biorefineries at small scale

During last decades, there has been a growing interest of decreasing the environmental impact generated by humans. This situation has been approached from different perspectives being the integral use of raw materials as one of the best alternatives. It was estimated that 3.7 × 10⁹ tonnes of agricultural residues are produced annually worldwide. Then, the integral use of feedstocks has been studied through the biorefinery concept. A biorefinery can be a promissory option for processing feedstocks in rural zones aiming to boost the techno-economic and social growth. However, many plants produced at small scale in rural zones without high industrial use contribute with residues usually not studied as raw materials for other processes. Cocoyam (Xanthosoma sagittifolium) is a plant grown extensively in tropical regions. Nigeria, China, and Ghana are the main producers with 1.3, 1.18, and 0.9 million tonnes/year, respectively. In Colombia, there are no technified crops, but it is used where it is grown mainly as animal feed. This plant consists of leaves, stem, and a tuber but the use is generally limited to the leaves, discarding the other parts. These discarded parts have great potential (lignocellulose and starch). This work proposes different processing schemes using the parts of the plant to obtain value-added products, and their techno-economic and environmental assessment. The simulation was performed with Aspen Plus and the economic package was used for the economic assessment. For the environmental assessment, Waste Algorithm Reduction of the U.S. EPA was implemented. The obtained results showed that the integral use of plants under a biorefinery scheme allows obtaining better techno-economic and environmental performance and that small-scale biorefineries can be a promissory option for boosting rural zones.

Biological processes for advancing lignocellulosic waste biorefinery by advocating circular economy

The actualization of a circular economy through the use of lignocellulosic wastes as renewable resources can lead to reduce the dependence from fossil-based resources and contribute to a sustainable waste management. The integrated biorefineries, exploiting the overall lignocellulosic waste components to generate fuels, chemicals and energy, are the pillar of the circular economy. The biological treatment is receiving great attention for the biorefinery development since it is considered an eco-friendly alternative to the physico-chemical strategies to increase the biobased product recovery from wastes and improve saccharification and fermentation yields. This paper reviews the last advances in the biological treatments aimed at upgrading lignocellulosic wastes, implementing the biorefinery concept and advocating circular economy.

Food waste generation and industrial uses: A review

Food waste is made up of materials intended for human consumption that are subsequently discharged, lost, degraded or contaminated. The problem of food waste is currently on an increase, involving all sectors of waste management from collection to disposal; the identifying of sustainable solutions extends to all contributors to the food supply chains, agricultural and industrial sectors, as well as retailers and final consumers. A series of solutions may be implemented in the appropriate management of food waste, and prioritised in a similar way to waste management hierarchy. The most sought-after solutions are represented by avoidance and donation of edible fractions to social services. Food waste is also employed in industrial processes for the production of biofuels or biopolymers. Further steps foresee the recovery of nutrients and fixation of carbon by composting. Final and less desirable options are incineration and landfilling. A considerable amount of research has been carried out on food waste with a view to the recovery of energy or related products. The present review aims to provide an overview of current debate on food waste definitions, generation and reduction strategies, and conversion technologies emerging from the biorefinery concept.