Sustainable production of bio-based chemicals and polymers via integrated biomass refining and bioprocessing in a circular bioeconomy context

Production of cost-competitive bioethanol and value-added co-products from distillers' grains: Techno-economic evaluation and environmental impact analysis

Here, Baijiu distillers' grains (BDGs) were employed in biorefinery development to generate value-added co-products and bioethanol. Through ethyl acetate extraction at a 1:6 solid-liquid ratio for 10 h, significant results were achieved, including 100 % lactic acid and 92 % phenolics recovery. The remaining BDGs also achieved 99 % glucan recovery and 81 % glucan-to-glucose conversion. Simultaneous saccharification and fermentation of remaining BDGs at 30 % loading resulted in 78.5 g bioethanol/L with a yield of 94 %. The minimum selling price of bioethanol varies from $0.149-$0.836/kg, contingent on the co-product market prices. The biorefinery processing of one ton of BDGs caused a 60 % reduction in greenhouse gas emissions compared to that of the traditional production of 88 kg corn-lactic acid, 70 kg antioxidant phenolics, 234 kg soybean protein, and 225 kg corn-bioethanol, along with emissions from BDG landfilling. The biorefinery demonstrated a synergistic model of cost-effective bioethanol production and low-carbon emission BDGs treatment.

Arabinose as an overlooked sugar for microbial bioproduction of chemical building blocks

The circular economy is anticipated to bring a disruptive transformation in manufacturing technologies. Robust and industrial scalable microbial strains that can simultaneously assimilate and valorize multiple carbon substrates are highly desirable, as waste bioresources contain substantial amounts of renewable and fermentable carbon, which is diverse. Lignocellulosic biomass (LCB) is identified as an inexhaustible and alternative resource to reduce global dependence on oil. Glucose, xylose, and arabinose are the major monomeric sugars in LCB. However, primary research has focused on the use of glucose. On the other hand, the valorization of pentose sugars, xylose, and arabinose, has been mainly overlooked, despite possible assimilation by vast microbial communities. The present review highlights the research efforts that have explicitly proven the suitability of arabinose as the starting feedstock for producing various chemical building blocks via biological routes. It begins by analyzing the availability of various arabinose-rich biorenewable sources that can serve as potential feedstocks for biorefineries. The subsequent section outlines the current understanding of arabinose metabolism, biochemical routes prevalent in prokaryotic and eukaryotic systems, and possible products that can be derived from this sugar. Further, currently, exemplar products from arabinose, including arabitol, 2,3-butanediol, 1,2,3-butanetriol, ethanol, lactic acid, and xylitol are discussed, which have been produced by native and non-native microbial strains using metabolic engineering and genome editing tools. The final section deals with the challenges and obstacles associated with arabinose-based production, followed by concluding remarks and prospects.

Life Cycle Assessment of Microbial 2,3-Butanediol Production from Brewer's Spent Grain Modeled on Pinch Technology

Microbial production of 2,3-butanediol (BDO) has received considerable attention as a promising alternate to fossil-derived BDO. In our previous work, BDO concentration >100 g/L was accumulated using brewer's spent grain (BSG) via microbial routes which was followed by techno-economic analysis of the bioprocess. In the present work, a life cycle assessment (LCA) was conducted for BDO production from the fermentation of BSG to identify the associated environmental impacts. The LCA was based on an industrial-scale biorefinery processing of 100 metric tons BSG per day modeled using ASPEN plus integrated with pinch technology, a tool for achieving maximum thermal efficiency and heat recovery from the process. For the cradle-to-gate LCA, the functional unit of 1 kg of BDO production was selected. One-hundred-year global warming potential of 7.25 kg CO₂/kg BDO was estimated while including biogenic carbon emission. The pretreatment stage followed by the cultivation and fermentation contributed to the maximum adverse impacts. Sensitivity analysis revealed that a reduction in electricity consumption and transportation and an increase in BDO yield could reduce the adverse impacts associated with microbial BDO production.

Sustainable Valorization of Bioplastic Waste: A Review on Effective Recycling Routes for the Most Widely Used Biopolymers

Plastics-based materials have a high carbon footprint, and their disposal is a considerable problem for the environment. Biodegradable bioplastics represent an alternative on which most countries have focused their attention to replace of conventional plastics in various sectors, among which food packaging is the most significant one. The evaluation of the optimal end-of-life process for bioplastic waste is of great importance for their sustainable use. In this review, the advantages and limits of different waste management routes-biodegradation, mechanical recycling and thermal degradation processes-are presented for the most common categories of biopolymers on the market, including starch-based bioplastics, PLA and PBAT. The analysis outlines that starch-based bioplastics, unless blended with other biopolymers, exhibit good biodegradation rates and are suitable for disposal by composting, while PLA and PBAT are incompatible with this process and require alternative strategies. The thermal degradation process is very promising for chemical recycling, enabling building blocks and the recovery of valuable chemicals from bioplastic waste, according to the principles of a sustainable and circular economy. Nevertheless, only a few articles have focused on this recycling process, highlighting the need for research to fully exploit the potentiality of this waste management route.

Thermophilic caproic acid production from grass juice by sugar-based chain elongation

Medium chain carboxylic acids (MCCA) such as caproic acid have a plethora of applications, ranging from food additives to bioplastics. MCCA can be produced via microbial chain elongation using waste and side-streams as substrates, a process that can be more sustainable than conventional production routes. Most chain elongation studies have focused on mesophilic conditions, with only two recent studies hinting at the possibility of thermophilic chain elongation, but a systematic study of its mechanisms is lacking. Here, we investigated thermophilic chain elongation from grass juice, to understand the effect of key operational parameters (pH, temperature, substrate) on the process performance and to establish the key microbial genera and their role in the system. The genus Caproiciproducens was identified as responsible for thermophilic chain elongation, and caproic acid production was most favorable at pH 6.0 and 50 °C among the conditions tested, reaching an average concentration of 3.4 g/L. Batch experiments showed that the substrate for caproic acid production were glucose and xylose, while lactic acid led to the production of only butyric acid. Fed-batch experiments showed that substrate availability and the presence of caproic acid in the system play a major role in shaping the profile of thermophilic chain elongation. The increase of the total sugar concentration by glucose addition (without changing the organic load) during continuous operation led to a microbial community dominated (75 %) by Caproiciproducens and increased by 76 % the final average caproic acid concentration to 6.0 g/L (13 g_COD/L) which represented 32 % (g/g) of the total carboxylic acids. The highest concentration achieved was 7.2 g/L (day 197) which is the highest concentration reported under thermophilic conditions thus far. The results of this work pave the way to the potential development of thermophilic systems for upgrading various underexplored abundant and cheap sugar-rich side-streams to caproic acid.

The development of recycling methods for bio-based materials - A challenge in the implementation of a circular economy: A review

This review focuses on the characteristics of the most widely used biopolymers that contain starch, polylactic acid, cellulose and/or polybutylene succinate. Because worldwide production of bio-based materials has grown dynamically, their waste is increasingly found in the existing waste treatment plants. The development of recycling methods for bio-based materials remains a challenge in the implementation of a circular economy. This article summarizes the recycling methods for bio-based materials, which, in the hierarchy of waste management, is much more desirable than landfilling. Several methods of recycling are available for the end-of-life management of bio-based products, which include mechanical (reuse of waste as a valuable raw material for further processing), chemical (feedstock recycling) and organic (anaerobic digestion or composting) ones. The use of chemical or mechanical recycling is less favourable, more costly and requires the improvement of systems for separation of bio-based materials from the rest of the waste stream. Organic recycling can be a sustainable alternative to those two methods. In organic recycling, bio-based materials can be biologically treated under aerobic or anaerobic conditions, depending on the characteristics of the materials. The choice of the recycling method to be implemented depends on the economic situation and on the properties of the bio-based products and their susceptibility to degradation. Thus, it is necessary to label the products to indicate which method of recycling is most appropriate.

Prospects and trends in bioelectrochemical systems: Transitioning from CO2 towards a low-carbon circular bioeconomy

Resource scarcity and climate change are the most quested topics in view of environmental sustainability. CO2 sequestration through bioelectrochemical systems is an attractive option for fostering bioeconomy development upon several value-added products generation. This review details the state-of-the-art of bioelectrochemical systems for resource recovery from CO2 along with various biocatalysts capable of utilizing CO2. Two bioprocesses (photo-electrosynthesis and chemolithoelectrosynthesis) were discussed projecting their potential for biobased economy development from CO2. Significance of adopting circular strategies for efficient resource recycling, intensifying product value, integrations/interlinking of multiple process chains for the development of circular bioeconomy were discussed. Existing constrains as well as outlook for near establishment of circular bioeconomy from CO2 is presented by weighing fore-sighted plans with current actions. Need for developing CO2-based circular bioeconomy via innovative business models by analyzing social, technical, environmental and product related aspects are also discussed providing a roadmap of gaps to pursue for attaining practicality.

An Updated Review on Prebiotics: Insights on Potentials of Food Seeds Waste as Source of Potential Prebiotics

Prebiotics are a group of biological nutrients that are capable of being degraded by microflora in the gastrointestinal tract (GIT), primarily Lactobacilli and Bifidobacteria. When prebiotics are ingested, either as a food additive or as a supplement, the colonic microflora degrade them, producing short-chain fatty acids (SCFA), which are simultaneously released in the colon and absorbed into the blood circulatory system. The two major groups of prebiotics that have been extensively studied in relation to human health are fructo-oligosaccharides (FOS) and galactooligosaccharides (GOS). The candidature of a compound to be regarded as a prebiotic is a function of how much of dietary fiber it contains. The seeds of fruits such as date palms have been reported to contain dietary fiber. An increasing awareness of the consumption of fruits and seeds as part of the daily diet, as well as poor storage systems for seeds, have generated an enormous amount of seed waste, which is traditionally discarded in landfills or incinerated. This cultural practice is hazardous to the environment because seed waste is rich in organic compounds that can produce hazardous gases. Therefore, this review discusses the potential use of seed wastes in prebiotic production, consequently reducing the environmental hazards posed by these wastes.

Life cycle assessment of microalgal biorefinery: A state-of-the-art review

Microalgal biorefineries represent an opportunity to economically and environmentally justify the production of bioproducts. The generation of bioproducts within a biorefinery system must quantitatively demonstrate its viability in displacing traditional fossil-based refineries. To this end, several works have conducted life cycle analyses on microalgal biorefineries and have shown technological bottlenecks due to energy-intensive processes. This state-of-the-art review covers different studies that examined microalgal biorefineries through life cycle assessments and has identified strategic technologies for the sustainable production of microalgal biofuels through biorefineries. Different metrics were introduced to supplement life cycle assessment studies for the sustainable production of microalgal biofuel. Challenges in the comparison of various life cycle assessment studies were identified, and the future design choices for microalgal biorefineries were established.

A comprehensive review on recent advancements in biodegradation and sustainable management of biopolymers

Recent years have seen upsurge in plastic manufacturing and its utilization in various fields, such as, packaging, household goods, medical applications, and beauty products. Due to various adverse impacts imposed by synthetic plastics on the health of living well-being and the environment, the biopolymers have been emerged out an alternative. Although, the biopolymers such as polyhydroxyalkanoates (PHA) are entirely degradable. However, the other polymers, such as poly (lactic acid) (PLA) are only partially degradable and often not biosynthesized. Biodegradation of the polymers using microorganisms is considered an effective bioremediation approach. Biodegradation can be performed in aerobic and anaerobic environments. In this context, the present review discusses the biopolymer production, their persistence in the environment, aerobic biodegradation, anaerobic biodegradation, challenges associated with biodegradation and future perspectives. In addition, this review discusses the advancement in the technologies associated with biopolymer production, biodegradation, and their biodegradation standard in different environmental settings. Furthermore, differences in the degradation condition in the laboratory as well as on-site are discussed.

Biorefinery development, techno-economic evaluation and environmental impact analysis for the conversion of the organic fraction of municipal solid waste into succinic acid and value-added fractions

The organic fraction of municipal solid waste (OFMSW) was used for biorefinery development within a circular bioeconomy context towards extraction of lipids/fats and proteins with 100% and 68% recovery yields, respectively, as well as succinic acid (SA) production. A nutrient-rich hydrolysate (89.1 g/L sugars) produced using crude enzymes derived via solid state fermentation of Aspergillus awamori, was employed in Actinobacillus succinogenes fermentation leading to 31.7 g_SA/L with 0.68 g/g yield and 0.67 g/L/h productivity. The SA minimum selling price ($1.13-2.39/kg_SA) considering 60,000 t_SA/year production varied depending on co-product market prices and OFMSW management fees. The biorefinery using 1000 kg OFMSW contributes 35% lower CO₂ emissions than conventional processes for the production of 105 kg vegetable oil, 87 kg vegetable protein and 206.4 kg fossil-SA considering also the CO₂ emissions due to OFMSW landfilling. The proposed OFMSW biorefinery leads to cost-competitive SA production with lower CO₂ emissions for OFMSW treatment.

Rational Engineering of Non-Ubiquinone Containing Corynebacterium glutamicum for Enhanced Coenzyme Q10 Production

Coenzyme Q₁₀ (CoQ₁₀) is a lipid-soluble compound with important physiological functions and is sought after in the food and cosmetic industries owing to its antioxidant properties. In our previous proof of concept, we engineered for CoQ₁₀ biosynthesis the industrially relevant Corynebacterium glutamicum, which does not naturally synthesize any CoQ. Here, liquid chromatography–mass spectrometry (LC–MS) analysis identified two metabolic bottlenecks in the CoQ₁₀ production, i.e., low conversion of the intermediate 10-prenylphenol (10P-Ph) to CoQ₁₀ and the accumulation of isoprenologs with prenyl chain lengths of not only 10, but also 8 to 11 isopentenyl units. To overcome these limitations, the strain was engineered for expression of the Ubi complex accessory factors UbiJ and UbiK from Escherichia coli to increase flux towards CoQ₁₀, and by replacement of the native polyprenyl diphosphate synthase IspB with a decaprenyl diphosphate synthase (DdsA) to select for prenyl chains with 10 isopentenyl units. The best strain UBI6-Rs showed a seven-fold increased CoQ₁₀ content and eight-fold increased CoQ₁₀ titer compared to the initial strain UBI4-Pd, while the abundance of CoQ₈, CoQ₉, and CoQ₁₁ was significantly reduced. This study demonstrates the application of the recent insight into CoQ biosynthesis to improve metabolic engineering of a heterologous CoQ₁₀ production strain.

Biotechnological production of specialty aromatic and aromatic-derivative compounds

Aromatic compounds are an important class of chemicals with different industrial applications. They are usually produced by chemical synthesis from petroleum-derived feedstocks, such as toluene, xylene and benzene. However, we are now facing threats from the excessive use of fossil fuels causing environmental problems such as global warming. Furthermore, fossil resources are not infinite, and will ultimately be depleted. To cope with these problems, the sustainable production of aromatic chemicals from renewable non-food biomass is urgent. With this in mind, the search for alternative methodologies to produce aromatic compounds using low-cost and environmentally friendly processes is becoming more and more important. Microorganisms are able to produce aromatic and aromatic-derivative compounds from sugar-based carbon sources. Metabolic engineering strategies as well as bioprocess optimization enable the development of microbial cell factories capable of efficiently producing aromatic compounds. This review presents current breakthroughs in microbial production of specialty aromatic and aromatic-derivative products, providing an overview on the general strategies and methodologies applied to build microbial cell factories for the production of these compounds. We present and describe some of the current challenges and gaps that must be overcome in order to render the biotechnological production of specialty aromatic and aromatic-derivative attractive and economically feasible at industrial scale.

Techno-economic evaluation and life cycle assessment of a biorefinery using winery waste streams for the production of succinic acid and value-added co-products

This study presents techno-economic evaluation and life cycle assessment of a novel biorefinery using the three main waste streams generated by wineries for the production of bio-based succinic acid (SA), crude phenolic-rich extract, grape-seed oil, calcium tartrate and crude tannin-rich extract. Process design has been employed for the estimation of material and energy balances and the sizing of unit operations. The Minimum Selling Price of succinic acid production within a winery waste biorefinery ranges from $1.23-2.76/kg_SA depending on the market price and the potential end-uses of the extracted fractions. The Global Warming Potential and the Abiotic Depletion Potential of winery waste valorisation through the proposed biorefinery are 1.47 kg CO₂-eq per kg dry waste and 25.2 MJ per kg dry waste, respectively. Biorefining of winery waste could lead to the development of a sustainable and novel bioeconomy business model with new market opportunities and efficient waste management.

Techno-economic risk assessment, life cycle analysis and life cycle costing for poly(butylene succinate) and poly(lactic acid) production using renewable resources

The sustainable production of poly(lactic acid) (PLA) or poly(butylene succinate) (PBS) from corn glucose syrup, corn stover and sugar beet pulp (SBP) have been assessed via process design, preliminary techno-economic evaluation, life cycle assessment and life cycle costing (LCC). Cost-competitive PLA and PBS production can be achieved in a SBP-based biorefinery, including separation of crude pectin-rich extract as co-product, leading to minimum selling prices of $1.14/kg_PLA and $1.37/kg_PBS. Acidification Potential, Eutrophication Potential and Human Toxicity Potential are lower when SBP is used. The LCC of PLA ($1.42/kg_PLA) and PBS ($1.72/kg_PBS) production from SBP are lower than biaxial oriented polypropylene (BOPP, $1.66/kg) and general purpose polystyrene (GPPS, $2.04/kg) at pectin-rich extract market prices of $3/kg and $4/kg, respectively. Techno-economic risk assessment via Monte-Carlo simulations showed that PLA and PBS could be produced from SBP at the market prices of BOPP ($1.4/kg) and GPPS ($1.72/kg) with 100% probability to achieve a positive Net Present Value at pectin-rich extract market prices of $3/kg and $4/kg, respectively. This study demonstrated that SBP-based biorefinery development ensures sustainable production of PLA and PBS as compared to fossil-derived counterparts and single product bioprocesses using glucose syrup and corn stover.

Bioplastics for a circular economy

Bioplastics - typically plastics manufactured from bio-based polymers - stand to contribute to more sustainable commercial plastic life cycles as part of a circular economy, in which virgin polymers are made from renewable or recycled raw materials. Carbon-neutral energy is used for production and products are reused or recycled at their end of life (EOL). In this Review, we assess the advantages and challenges of bioplastics in transitioning towards a circular economy. Compared with fossil-based plastics, bio-based plastics can have a lower carbon footprint and exhibit advantageous materials properties; moreover, they can be compatible with existing recycling streams and some offer biodegradation as an EOL scenario if performed in controlled or predictable environments. However, these benefits can have trade-offs, including negative agricultural impacts, competition with food production, unclear EOL management and higher costs. Emerging chemical and biological methods can enable the 'upcycling' of increasing volumes of heterogeneous plastic and bioplastic waste into higher-quality materials. To guide converters and consumers in their purchasing choices, existing (bio)plastic identification standards and life cycle assessment guidelines need revision and homogenization. Furthermore, clear regulation and financial incentives remain essential to scale from niche polymers to large-scale bioplastic market applications with truly sustainable impact.

Microbial production and recovery of hybrid biopolymers from wastes for industrial applications- a review

Agro-industrial wastes to be a global concern since agriculture and industrial processes are growing exponentially with the fast increase of the world population. Biopolymers are complex molecules produced by living organisms, but also found in many wastes or derived from wastes. The main drawbacks for the use of polymers are the high costs of the polymer purification processes from waste and the scale-up in the case of biopolymer production by microorganisms. However, the use of biopolymers at industrial scale for the development of products with high added value, such as food or biomedical products, not only can compensate the primary costs of biopolymer production, but also improve local economies and environmental sustainability. The present review describes some of the most relevant aspects related to the synthesis of hybrid materials and nanocomposites based on biopolymers for the development of products with high-added value.

Modification of Poly(lactic acid) by the Plasticization for Application in the Packaging Industry

Plastic products, especially in the packaging industry, have become the main commodities penetrating virtually every aspect of our lives. Unfortunately, their omnipresence is not neutral to the natural environment. Pollution in the form of microplastics is a global problem. Therefore, green technologies that enter into the circular economy become an important topic. As part of the research work, the modification of poly(lactic acid) has been studied for use in the packaging industry. Due to its intrinsic rigidity, plasticizing substances had to be introduced in PLA in order to improve its plastic deformability. Both high-molecular compounds such as ethoxylated lauryl alcohol, block copolymer of ethylene oxide and propylene oxide, and ethoxylated stearic acid as well as low-molecular compounds such as di-2-ethylhexyl adipate, di-2-ethylhexyl sebacate, and triethyl citrate were used. The samples extruded from plasticized polymers were characterized using differential scanning calorimetry, thermal gravimetric analysis, and mechanical properties including Young’s modulus. The melt flow rate (MFR) and molar mass distribution were determined. For all modified samples the glass transition temperature, depending on the plasticizer used, was shifted towards lower values compared to the base polymer. The best result was obtained for di-2-ethylhexyl adipate (ADO) and di-2-ethylhexyl sebacate (SDO). The elongation at break increased significantly for ADO at about 21%. The highest elongation was obtained for SDO (about 35%), although it obtained a higher glass temperature. The degradation of the polymer was not observed for both plasticizers. For these plasticizers (ADO and SDO) it also lowered Young’s module by about 26%, and at the infrared spectrum deformation of peaks were observed, which may indicate the interaction of the ester carbonyl group of PLA with plasticizers. Therefore it can be concluded that they are good modifiers. The selected plasticizers that are used in the production of food contact materials, in particular in the production of PVC (polyvinyl chloride) food films, also exhibited great potential to be applied to PLA food films, and exhibit better properties than the citrate, which are indicated in many publications as PLA plasticizers.

Influence of the Initial Sugar Concentration and Supplementation with Yeast Extract on Succinic Acid Fermentation in a Lactose-Based Medium

The aim of this study was to investigate the production of succinic acid from lactose concentrate, a by-product of cheese-making, using Actinobacillus succinogenes and Basfia succiniciproducens. Although the ability of these strains to metabolize different sugars is already known, their application in the conversion of lactose bears high potential for optimization. With regard to B. succiniciproducens, this approach is completely novel. In particular, the effect of the medium’s sugar concentration as well as the ability of its supplementation with yeast extract to prevent a lack of essential nutrient proteins and vitamins was examined. Lactose-based media containing sugar concentrations of between 20 and 65 g L−1 and 5 g L−1 of yeast extract were fermented, with both strains showing comparable performances. The best results in terms of succinic acid yield and acid concentration—0.57 g g−1 initial sugar and 23 g L−1—were achieved at an initial sugar concentration of 43 g L−1. The necessity of yeast extract was demonstrated using the sugar-optimized medium without supplementation. As a result, the yield and concentration of succinic acid dropped to 0.34 g g−1 and 13 g L−1 and the sugar consumption decreased from more than 99 to less than 55%. Therefore, the supplementation amount of 5 g L−1 of yeast extract can be regarded as well-balanced.

Effect of PLA Active Packaging Containing Monoterpene-Cyclodextrin Complexes on Berries Preservation

Blackberries and raspberries are highly perishable and fragile products, which limits their shelf life. The effect of biodegradable active packaging of blackberries and raspberries containing 2.5% and 5.0% weight (wt%) of thymol or carvacrol complexed in β-cyclodextrins (β-CDs), successively added to poly (lactic acid) (PLA), and melt-processed by injection molding was evaluated under stored conditions at 4 °C for 21 days, using as reference commercial clamshell and PLA package control samples. Thus, physicochemical, headspace, microbiological, and sensory quality studies were carried out in order to compare the efficacy of the different packages. Concerning weight loss, color, and total phenolic and soluble solids content, significant differences were detected when compared with commercial clamshell packaging. The results show that the PLA packages containing thymol and carvacrol complexes maintained the color, weight, and phenolic content of berries until day 21, with a score up to 45% better compared to commercial clamshell. The headspace analysis detected 101 mg L⁻¹ (ppm) of thymol and 35 ppm of carvacrol on the first day of refrigeration; these concentrations decreased with time. This release mechanism of carvacrol and thymol into the PLA package modified the initial atmosphere composition. After 21 days of storage, the berries had 4.25 degrees of acceptance, without adverse perception of aroma or flavor for both carvacrol and thymol compounds. A general microbial inhibition was observed for yeast and molds, which increased with the concentration of monoterpene in PLA packages, and showed an inhibition of 3.5 log units for PLA packages containing thymol, and of 3 log units for those containing carvacrol. Overall results show that PLA/β-CD-thymol 5.0% packages prolonged raspberries’ and blackberries’ shelf life by one more week at 4 °C, compared with commercial clamshell packaging.

Mechanically Strong Polyurethane Composites Reinforced with Montmorillonite-Modified Sage Filler (Salvia officinalis L.)

Rigid polyurethane (PUR) foams reinforced with 1, 2, and 5 wt.% of salvia filler (SO filler) and montmorillonite-modified salvia filler (MMT-modified SO filler) were produced in the following study. The impact of 1, 2, and 5 wt.% of SO filler and MMT-modified SO filler on the morphological, chemical, and mechanical properties of PUR composites were examined. In both cases, the addition of 1 and 2 wt.% of SO fillers resulted in the synthesis of PUR composites with improved physicomechanical properties, while the addition of 5 wt.% of SO fillers resulted in the formation of PUR composites with a less uniform structure and, therefore, some deterioration in their physicomechanical performances. Moreover, the results showed that the modification of SO filler with MMT improved the interphase compatibility between filler surface and PUR matrix. Therefore, such reinforced PUR composites were characterized by a well-developed closed-cell structure and improved mechanical, thermal, and flame-retardant performances. For example, when compared with reference foam, the addition of 2 wt.% of MMT-modified SO filler resulted in the formation of PUR composites with greater mechanical properties (compressive strength, flexural strength) and improved dynamic-mechanical properties (storage modulus). The PUR composites were characterized by better thermal stability as well as improved flame retardancy-e.g., decreased peak rate of heat release (pHRR), reduced total smoke release (TSR), and increased limiting oxygen index (LOI).

Techno-economic evaluation and life-cycle assessment of poly(3-hydroxybutyrate) production within a biorefinery concept using sunflower-based biodiesel industry by-products

This study presents techno-economic evaluation of a biorefinery concept using biodiesel industry by-products (sunflower meal and crude glycerol) to produce poly(3-hydroxybutyrate) (PHB), crude phenolic extracts (CPE) and protein isolate (PI). The PHB production cost at two annual production capacities ($12.5/kg for 2,500 t PHB/year and $7.8/kg for 25,000 t PHB/year) was not cost-competitive to current PHB production processes when the revenues derived from co-products were not considered. Sensitivity analysis projected the economic viability of a biorefinery concept that could achieve a minimum selling price of $1.1/kg PHB similar to polypropylene. The annual PHB production capacity and the identification of marketable end-uses with respective market prices for the co-products CPE and PI were crucial in attaining process profitability. Greenhouse gas emissions (ca. 0.64 kg CO_2-eq/kg PHB) and abiotic depletion potential (61.7 MJ/kg PHB) were lower than polypropylene. Biorefining of sunflower meal and crude glycerol could lead to sustainable PHB production.

Potential of time-stepping stochastic models as tools for guiding the design and operation of processes for the enzymatic hydrolysis of polysaccharides - A review

Processes for the enzymatic hydrolysis of polysaccharides in biorefineries are becoming increasingly important. The complex network of reactions involved in polysaccharide hydrolysis can be described by stochastic models that advance in steps of time. Such models have the potential to be important tools for guiding process design and operation, and several have been developed over the last two decades. We evaluate these models. Many of the current stochastic models for the hydrolysis of colloidal polysaccharides use empirical parameters that have no recognized biological meaning. Only one model uses classical parameters of enzyme kinetics, namely specificity constants and saturation constants. Recent stochastic models for the hydrolysis of insoluble cellulose give valuable insights into the molecular-level phenomenon that limit hydrolysis rates. We conclude that, if stochastic models of enzymatic polysaccharide hydrolysis are to become widely used tools for guiding process development, then further improvements are required.

Biodiesel production using microbial lipids derived from food waste discarded by catering services

Biodiesel production using microbial oil derived from food waste discarded by the hospilatity sector could provide a sustainable replacement for diesel fuel. Discarded potato peels were used in solid-state fermentations of Aspergillus awamori for the production of glucoamylase (30 U/g) and protease (50 U/g). Hospitality food waste hydrolysis led to 98% (w/w) starch to glucose conversion yields. Crude hydrolyzates were used in shake flask fermentations with the oleaginous yeast Rhodosporidium toruloides Y-27012 leading to 32.9 g/L total dry weight (TDW) with 36.4% (w/w) intracellular lipid content. Fed-bath bioreactor cultures resulted in TDW of 53.9 g/L and lipid concentration of 26.7 g/L. Principal component analysis showed a fatty acid profile similar to soybean oil and solid food waste oil. Microbial oil was transesterified into biodiesel with satisfactory performance considering the European standard EN 14214. This work demonstrated that valorization of food waste for biodiesel production is feasible.

Lignin-Based Polyols with Controlled Microstructure by Cationic Ring Opening Polymerization

Lignin-based polyols (LBPs) with controlled microstructure were obtained by cationic ring opening polymerization (CROP) of oxiranes in an organosolv lignin (OL) tetrahydrofuran (THF) solution. The control on the microstructure and consequently on the properties of the LBPs such as hydroxyl number, average molecular weight, melting, crystallization and decomposition temperatures, are crucial to determine the performance and application of the derived-products. The influence of key parameters, for example, molar ratio between the oxirane and the hydroxyl groups content in OLO, initial OL concentration in THF, temperature, specific flow rate and oxirane nature has been investigated. LBPs with hydroxyl numbers from 35 to 217 mg KOH/g, apparent average M_w between 5517 and 52,900 g/mol and melting temperatures from −8.4 to 18.4 °C were obtained. The CROP procedure allows obtaining of tailor-made LBPs for specific applications in a very simple way, opening the way to introduce LBPs as a solid alternative to substitute currently used fossil-based polyols.

Enzymes and biopolymers. The opportunity for the smart design of molecular delivery systems

Enzymes exhibit a tremendous potential due to the catalytic activity in response to physiological conditions and specific microenvironments. Exploiting these properties in combination with the versatility of biopolymers, a fascinating field for the rational development of a new class of "smart" delivery systems for therapeutic molecules is proposed. Many strategies have been recently developed to produce matrices with the desirable properties of molecular release, and enzymes could be playing a relevant role in modify the chemical composition of the polymers, the porosity and surface area of the matrices and modulate the kinetic of controlled release. Enzyme based computational systems have appeared as a relevant complementary tool to design novel smart bioactive matrices for programmable drug delivery. The present review is reporting the recent advances and projections of smart biopolymeric matrices activated by enzymes for sustained release of therapeutic molecules, highlighting various applications in the area of advanced drug delivery.

Analysis of the Circular Economic Production Models and Their Approach in Agriculture and Agricultural Waste Biomass Management

As of now, circular economic production models of the circular economy (CEPMs), which include circular economy, bioeconomy, and circular bioeconomy, are among the main tools characterizing development policies in different countries. During the last five years, policies and strategies regarding CEPMs have promoted and contributed to the development of research on this topic. The evolution and most relevant aspects of the three CEPMs previously mentioned have been analyzed from a sample of 2190 scientific publications obtained from the Scopus database. Bibliometric analysis has been used to evaluate the approach of these models in agriculture and to introduce the ways in which they address the management of agricultural waste biomass (AWB). Results show that the circular economy is the most studied and prioritized model in China and most European countries, with the UK leading the way. Germany leads in topics related to the bioeconomy. The management policies and strategies of the circular bioeconomy are key to promoting research focused on AWB valorization since bioenergy and/or biofuel production continue to be a priority.

Two Food Waste By-Products Selectively Stimulate Beneficial Resident Citrus Host-Associated Microbes in a Zero-Runoff Indoor Plant Production System

The global production of food waste is a far-reaching problem with sizable financial, ethical, social, and environmental costs. Over 66 million tons of food waste is produced annually in the United States alone. This waste can be converted into valuable digestate by-products that promote a circular economy within agri-food systems. The present work investigated the use of two liquid digestates of microaerobic fermentation from mixed food waste and beer mash, respectively, as biostimulants for non-bearing citrus plants (nursery stock) grown in a zero-runoff greenhouse system with recirculating irrigation. The digestates' impact on the structure and diversity of the microbiota was determined on the irrigation water, soil, leaves, roots, and rhizosphere of citrus plants. A combination of culture-dependent (selective media) and culture-independent approaches (Next-Generation Sequencing) was used to assess the composition of the microbial communities and to single out the presence of foodborne pathogens. Our results suggest that the use of digestates is safe (i.e., no human or plant pathogens were present in the digestates or enriched in the plant production system following amendments). Digestates application to the irrigation water reduced the bacterial diversity within 24–48 h and selectively and significantly stimulated beneficial resident host-associated microorganisms (Pseudomonas putida) by two to three orders of magnitude. Carbon dynamics were analyzed in the nutrient solutions by measuring dissolved organic carbon and characterizing carbon species through gas chromatography-electron ionization-mass spectrometry. Our results indicate that dissolved organic carbon in the recirculating irrigation water spikes after each digestate amendment and it is quickly metabolized by bacteria, plateauing 24 h after application. Soil carbon, nitrogen, and nutrient dynamics were also analyzed, and results suggest that digestates increased the concentration of some plant nutrients in soils without causing a surge of potentially toxic elements. This study represents a proof-of-concept for the safe re-use of organic wastes, from farming and consumers, in agriculture. Implementing this type of integrated plant production system could reduce the environmental impact of food waste and benefit the public by improving soil health, reducing agricultural footprint, and increasing crop fitness by deploying a method based on a circular economy and sustainable food production approaches.

Rethinking and optimising plastic waste management under COVID-19 pandemic: Policy solutions based on redesign and reduction of single-use plastics and personal protective equipment

Plastics have been on top of the political agenda in Europe and across the world to reduce plastic leakage and pollution. However, the COVID-19 pandemic has severely disrupted plastic reduction policies at the regional and national levels and induced significant changes in plastic waste management with potential for negative impacts in the environment and human health. This paper provides an overview of plastic policies and discusses the readjustments of these policies during the COVID-19 pandemic along with their potential environmental implications. The sudden increase in plastic waste and composition due to the COVID-19 pandemic underlines the crucial need to reinforce plastic reduction policies (and to implement them into action without delays), to scale up in innovation for sustainable and green plastics solutions, and to develop dynamic and responsive waste management systems immediately. Policy recommendations and future research directions are discussed.

Multiproduct biorefinery based on almond shells: Impact of the delignification stage on the manufacture of valuable products

In this work, an integral valorisation of almond shells through a biorefinery approach was studied. The three main components of almond shells were extracted, isolated and characterised. The autohydrolysis process permitted the extraction of the hemicellulosic fraction obtaining a liquor rich in xylooligosaccharides (22.12 g/L). Then, two different delignification processes, alkaline and organosolv treatments, were proposed to obtain a very high purity lignin (≈90%) which could be further valorised for a wide variety of applications. The valorisation of the high cellulosic content of the delignified solids was carried out using two different methods. On the one hand, producing cellulose nanocrystals and on the other hand obtaining glucose by an enzymatic hydrolysis as well as a spent solid mainly composed by lignin (≈78 wt%). Thus, the proposed biorefinery approach could contribute to a circular economy as all the main components of the almond shells could be revalorised by environmentally friendly procedures.

Bioeconomy - present status and future needs of industrial value chains

The necessary reduction of greenhouse gas emissions requires a comprehensive shift from fossil to renewable raw materials. This is accompanied by a fundamental reorganization of the value chains of the energy sectors and large parts of the manufacturing industry. In the long term, bio-based industrial raw materials will be processed preferentially by the chemical industry. In order to use the raw materials as fully as possible, sectors that support cascade use and the recycling of by-products and products after use will gain in importance. These are in particular the waste management and energy sectors, which will be integrated into the circular value chains of the bioeconomy. The industrial realization of these value chains depends essentially on the legal framework conditions, which must be developed further accordingly.

Batch and Continuous Lactic Acid Fermentation Based on A Multi-Substrate Approach

The utilisation of waste materials and industrial residues became a priority within the bioeconomy concept and the production of biobased chemicals. The aim of this study was to evaluate the feasibility to continuously produce L-lactic acid from different renewable substrates, in a multi-substrate strategy mode. Based on batch experiments observations, Bacillus coagulans A534 strain was able to continuously metabolise acid whey, sugar beet molasses, sugar bread, alfalfa press green juice and tapioca starch. Additionally, reference experiments showed its behaviour in standard medium. Continuous fermentations indicated that the highest productivity was achieved when molasses was employed with a value of 10.34 g·L⁻¹·h⁻¹, while the lactic acid to sugar conversion yield was 0.86 g·g⁻¹. This study demonstrated that LA can be efficiently produced in continuous mode regardless the substrate, which is a huge advantage in comparison to other platform chemicals.

A novel and efficient approach to obtain lignin-based polyols with potential industrial applications

Current work is paving the way to manufacture, by new benign route, lignin-based polyols families with application in biopolymers synthesis.