Sustainable blueberry waste recycling towards biorefinery strategy and circular bioeconomy: A review

The Green Extraction of Blueberry By-Products: An Evaluation of the Bioactive Potential of the Anthocyanin/Polyphenol Fraction

In the context of a circular economy, this study explores the valorization of blueberry pomace (BP) as a source of bioactive compounds using sustainable extraction methods. Microwave-assisted extraction (MAE) and microwave-assisted subcritical water extraction (MASWE) were employed to obtain two distinct fractions: MAE 1° and MASWE 2°. The first extract, MAE 1°, obtained at 80 °C, had a high total anthocyanin content (21.96 mgCya-3-glu/gextract), making it suitable as a natural pigment. Additionally, MAE 1° exhibited significant enzyme inhibition, particularly against α-amylase and β-glucosidase, suggesting potential anti-diabetic and anti-viral applications. The second extract, MASWE 2°, obtained at 150 °C, contained a higher total phenolic content (211.73 mgGAE/gextract) and demonstrated stronger antioxidant activity. MASWE 2° showed greater inhibition of acetylcholinesterase and tyrosinase, indicating its potential for use in Alzheimer's treatment, skincare, or as a food preservative. MASWE 2° exhibited cytotoxicity against HeLa cells and effectively mitigated H2O2-induced oxidative stress in HaCat cells, with MAE 1° showing similar but less pronounced effects. A tested formulation combining MAE 1° and MASWE 2° extracts in a 3:2 ratio effectively enhanced anthocyanin stability, demonstrating its potential as a heat-stable pigment. The extract characteristics were compared with a conventional method (MeOH-HCl in reflux condition), and the protocol's sustainability was assessed using several green metric tools, which provided insights into its environmental impact and efficiency.

Compressed fluid-based technology for downstream isolation of bluish anthocyanin-derived pigments obtained from blueberry surplus

A dynamic compressed fluid-based separation process combining carbon dioxide and ethanol was explored to isolate portisins previously hemi-synthesized from blueberry surplus anthocyanins. The influence of process parameters such as pressure (100-500 bar), temperature (40-60 °C), and ethanol content in the compressed fluid mixture (20-50 wt%) on extraction yield, portisins yield, and portisins content in the extract was investigated. The two-step isolation process includes (1) a first step at 100 bar, 60 °C, and 20 wt% ethanol content in the compressed fluid mixture to remove the low polarity compounds; and (2) a second step at 500 bar, 40 °C, and 100 wt% ethanol to recover portisins, resulting in a 1.5-fold increase in portisins content. The performance of the two-step separation process was compared to centrifugal partitional chromatography and conventional reverse phase liquid chromatography already reported in terms of portisins content in the extract, process throughput, process efficiency, and total solvent used. The two-step separation process decreased the total solvent used, although with a decrease in the throughput and efficiency. Nevertheless, the choice of the best separation technology depends on the application, as these techniques result in different portisins purities. Overall, this study contributed to a scalable and more sustainable process for natural colorant production, specifically focusing on blue pigments, with several industrial applications.

Reuse of composted food waste from rural China as vermicomposting substrate: effects on earthworms, associated microorganisms, and economic benefits

ABSTRACTAerobic composting of food waste (FW) from rural China using a composting device results in a substantial financial burden on the government. This study aimed to assess the feasibility of mitigating this cost using vermicomposting of composted FW. The specific aims were to elucidate the effects of composted FW on earthworm growth and reproduction, reveal the changes in the physical and chemical properties of earthworm casts during vermicomposting, identify the microbial community structure associated with vermicomposting, and perform a financial analysis based on the yield of earthworms and earthworm casts. Mixing composted FW and mature cow dung in an equal ratio achieved the highest earthworm reproduction rate, where 100 adult earthworms produced 567 juvenile earthworms and 252 cocoons in 40 d. Earthworms reduce salt content of vermicomposting substrates by assimilating Na+ and promoting humification by transforming humin into humic and fulvic acid, thus producing earthworm casts with a high generation index > 80%. When composted FW was added to a vermicomposting substrate, a distinctive microbial community structure with alkaliphilic, halophilic, and lignocellulolytic microorganisms dominated the microflora. The dominant bacterial species was Saccharopolyspora rectivirgula, and the dominant fungal species changed from Kernia nitida to Coprinopsis scobicola. Furthermore, microbial genes for refractory organic matter and fat degradation were observed in Vibrio cholerae, Kernia nitida, and Coprinopsis scobicola. Financial analysis showed that vermicomposting has the potential to reduce the cost associated with FW disposal from $ 57 to $ 18/t.

In Vitro Antibacterial and Antioxidative Activity and Polyphenolic Profile of the Extracts of Chokeberry, Blackcurrant, and Rowan Berries and Their Pomaces

The chemical composition of berries and berry pomaces is diverse, containing polyphenolic components that may have both antibacterial and antioxidative properties. In the present study, in vitro antibacterial effect of the extracts of chokeberry, blackcurrant, and rowan berries and berry pomaces against L. monocytogenes, S. aureus, E. coli, and C. jejuni was studied. In addition, the polyphenolic profile and antioxidant activity of these extracts were investigated. The polyphenolic profiles in the aqueous and 30% ethanolic extracts were determined chromatographically by HPLC-MS, and the total polyphenol content was estimated spectrophotometrically by HPLC-DAD-UV. The minimal inhibition concentrations (MICs) of the extracts against tested bacteria were determined by the broth microdilution method. The content of total polyphenols was highest and good antioxidative properties of the extracts were determined for chokeberry and blackcurrant berries and their pomaces. The highest proportions of total quercetin derivatives and anthocyanins were found in the extracts of chokeberry berry/pomace and blackcurrant berry/pomace, respectively. The sensitivity of tested microbes to the extracts of berries and berry pomaces was as follows: S. aureus > L. monocytogenes > E. coli and C. jejuni. In vitro antibacterial activity of tested extracts depended on the extraction solvent, mainly for the ethanolic extracts. Findings suggest that chokeberry and blackcurrant berries and their pomaces can be used as a good source of polyphenols with antioxidative properties, and they also have antibacterial activity against some foodborne pathogenic bacteria. It is important that the valuable compounds are extracted from juice press residues before their disposal.

Comparisons in phytochemical components and in vitro digestion properties of corresponding peels, flesh and seeds separated from two blueberry cultivars

Highbush blueberries (HB) and rabbiteye blueberries (RB) were separated into peels, flesh, and seeds to assess the compositions of nutriment, anthocyanins, soluble sugars and fatty acids, and the in vitro digesting abilities. Total phenolics contents (TPC) of 51-56 mg GAE/g DW were found in blueberry peels. Compared with HB peels, RB peels showed much higher TPC, but only contained 35 phenolics and lacked peonidin-3-O-rutinoside. Glucose, fructose, and sucrose were all present in HB and RB, but RB flesh had a higher acid-sugar ratio. Unsaturated fatty acid concentrations in HB and RB seeds were comparable (26.65 and 26.43 mg/g, respectively). However, HB seeds have 35 fatty acids, but RB seeds lacked cis-4,7,10,13,16,19-docosahexaenoic acid and cis-10-pentadecenoic acid. The in vitro digestion test showed that the whole fruit/peels/flesh of RB had a higher recovery and bioavailability index of phenolics and anthocyanins. Therefore, the reuse of blueberry pomace needs to be emphasized.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01326-w.

Waste-derived nanobiochar: A new avenue towards sustainable agriculture, environment, and circular bioeconomy

The greatest challenge for the agriculture sector in the twenty-first century is to increase agricultural production to feed the burgeoning global population while maintaining soil health and the integrity of the agroecosystem. Currently, the application of biochar is widely implemented as an effective means for boosting sustainable agriculture while having a negligible influence on ecosystems and the environment. In comparison to traditional biochar, nano-biochar (nano-BC) boasts enhanced specific surface area, adsorption capacity, and mobility properties within soil, allowing it to promote soil properties, crop growth, and environmental remediation. Additionally, carbon sequestration and reduction of methane and nitrous oxide emissions from agriculture can be achieved with nano-BC applications, contributing to climate change mitigation. Nonetheless, due to cost-effectiveness, sustainability, and environmental friendliness, waste-derived nano-BC may emerge as the most viable alternative to conventional waste management strategies, contributing to the circular bioeconomy and the broader goal of achieving the Sustainable Development Goals (SDGs). However, it's important to note that research on nano-BC is still in its nascent stages. Potential risks, including toxicity in aquatic and terrestrial environments, necessitate extensive field investigations. This review delineates the potential of waste-derived nano-BC for sustainable agriculture and environmental applications, outlining current advancements, challenges, and possibilities in the realms from a sustainability and circular bioeconomy standpoint.

Isolation of bluish anthocyanin-derived pigments obtained from blueberry surplus using centrifugal partition chromatography

Replacement of synthetic colorants with natural ones is a current marketing trend. Nevertheless, the naturally occurring blue color is rare compared to other colours. In this work, centrifugal partition chromatography (CPC) process was developed as a more efficient and sustainable alternative to reversed phase column chromatography (RP-CC) for the preparative-scale purification of portisins. The strategy began with the extraction of anthocyanins from blueberry surplus and hemi-synthesis of respective portisins. Then, the CPC method development started with the biphasic solvent system selection followed by the optimization of the operating parameters and ended up with a comparison with RP-CC. Aiming at maximizing the portisin content, process throughput, efficiency, and minimizing the environmental risk factor, the effect of sample load (100-500 mg/100 mL of column volume), mobile phase flow rate (10-20 mL/min), and rotation speed (1000-1600 rpm) was evaluated. The two-phase solvent system consisted of tert‑butyl‑methyl ether, n-butanol, acetonitrile, and water (volume ratio 2:2:1:5) acidified with 0.1 vol.% of HCl was selected. The best conditions were 464 mg of sample/100 mL of column volume, 20 mL/min of mobile phase flow rate, and 1600 rpm of rotation speed at reversed phase mode, allowing the purification of portisins by 5-fold. Compared to the RP-CC, the CPC process efficiency was 2.4 times higher, while the CPC process environmental risk factor was 5.5 times lower. Overall, this study suggests that CPC can be considered an effective, and sustainable alternative process for the preparative isolation of portisins. With this purification approach, the blueberry surplus has been valorized and a naturally derived product has been prepared, allowing its subsequent use as a natural blue colorant.

Optimisation of Polyphenols Extraction from Wild Bilberry Leaves-Antimicrobial Properties and Stability Studies

Polyphenolic extracts from natural sources have received great interest due to their beneficial properties for human health. A method to reduce their variability is to use the design of experiments which allows a limited number of experiments to be performed while exploring the experimental space. Firstly, a 23-full factorial model was used to investigate the polyphenols extraction from wild bilberry leaves. Spectrophotometric data (the content of polyphenols, flavonoids, chlorophyll and radical scavenger activity) and extraction yield were used as responses, and six statistical models were determined depending on the two numerical factors (temperature and alcohol % of ethanol-water mixture) being significant (p < 0.05) in all cases. Numerical optimisation performed by Design Expert 13 software correlates well with the chemical profile determined by high-performance liquid chromatography and the amount of the polyphenol. Afterwards, under the optimised conditions, an extract was prepared in three extraction steps for which composition, chemical stability and antimicrobial properties were evaluated. The antimicrobial potential of the extract was compared with that of the standard compounds (rutin and chlorogenic acid), and the results supported a synergistic effect of the extract components.

Valorization of tropical fruits waste for production of commercial biorefinery products - A review

Tropical fruit wastes (TFW) are considered as the major source of food and nutrition in the topical countries. In the recent years, modernization of agriculture has increased the tropical fruit production. Higher fruit production led to an increasing abundance in the tropical fruit waste. In general, the tropical fruit waste has no economic value and ends up in landfill. But in recent years it was observed that the tropical fruit waste can be valorized to produce value-added products ranging from compost, phytochemicals, and food products to biofuels. The tropical fruit waste has great potential to produce useful products in tropical areas. This review literature is an endeavor to understand the major tropical fruit wastes and their composition. The review presents a detailed investigation on tropical fruit waste composition, its conversion potential, role of microbes in waste valorization, production of commercially valuable products and future perspectives in waste valorization.

Ultrasound-Assisted Extraction of Blackberry Seed Oil: Optimization and Oil Characterization

Ultrasound-assisted extraction (UAE) was applied to extract oil from blackberry (BB) seeds. The effect of UAE conditions on oil recovery and quality was investigated. Favorable experimental conditions (ultrasound intensity (UI), extraction temperature, and time) were investigated using response surface methodology (RSM). A Box–Behnken design was used to predict optimized conditions for BB seed oil extraction. These conditions were as follows: 13.77 W/cm2 UI, 45 °C extraction temperature, and 15 min extraction time. The experimental value obtained for extraction efficiency under optimal conditions was 87 ± 0.34%, in good agreement with the optimized predicted value. UAE does not affect the oil composition and confers higher antioxidant values in BB seed oil in comparison with Soxhlet extraction.

Filamentous fungi for sustainable vegan food production systems within a circular economy: Present status and future prospects

Filamentous fungi serve as potential candidates in the production of different value-added products. In the context of food, there are several advantages of using filamentous fungi for food. Among the main advantages is that the fungal biomass used food not only meets basic nutritional requirements but that it is also rich in protein, low in fat, and free of cholesterol. This speaks to the potential of filamentous fungi in the production of food that can substitute animal-derived protein sources such as meat. Moreover, life-cycle analyses and techno-economic analyses reveal that fungal proteins perform better than animal-derived proteins in terms of land use efficiency as well as global warming. The present article provides an overview of the potential of filamentous fungi as a source of food and food supplements. The commercialization potential as well as social, legal and safety issues of fungi-based food products are discussed.

Concept for the valorization of cereal processing waste: Recovery of phenolic acids by using waste-derived tetrahydrofurfuryl alcohol and biochar

Valorization of agro-food waste by converting it into a renewable resource plays a crucial role in a bio-based circular economy. Therefore, this study was designed to evaluate the suitability of distillery stillage (DS), which comes from alcohol production from cereals, for producing value-added products that can be used synergistically. The main objective was to investigate the usefulness of two substances for the recovery of phenolic acids, which have antioxidant activity, from the liquid fraction of DS: namely, tetrahydrofurfuryl alcohol (THFA) as a solvent and biochar as an adsorbent, both produced from the solid fraction of cereal processing waste. The effect of THFA concentration (80 and 100%) on phenolic acid yield in ultrasound-assisted extraction was studied. The solubilization predictions of phenolic compounds by the Hansen solubility parameters were in accordance with the experimental results: the yield of phenolic acids in the extracts was highest (3.76 μg g^-1 dry mass) with 80% THFA. Among the extracted phenolic acids, hydroxycinnamic acids predominated over hydroxybenzoic acids, which may affect the bioactive properties of the extracts and their future applications for industrial purposes. Phenolic acids from the extracts were adsorbed on 17-170 g biochar L^-1 and desorbed into water at 40-60 °C. The phenolic acid recovery was highest (∼92%) when the biochar dose was 85 g L^-1 and when desorption was performed at 50 °C. After adsorption/desorption, ∼95% of the antioxidant activity of the phenolic acids in the extracts was maintained. As biochar has a smaller specific surface area than commercial powdered activated carbon (PAC), the biochar dose should be about 5 times higher than an equivalent PAC dose for adsorption efficiency above 90%.

Recent advances in lignocellulosic and algal biomass pretreatment and its biorefinery approaches for biochemicals and bioenergy conversion

As the global demand for sustainable energy increases, lignocellulosic (such as agricultural residues, forest biomass, municipal waste, and dedicated energy crops) and algal (including macroalgae and microalgae) biomass have attracted considerable attention, because of their high availability of carbohydrates. This is a potential feedstock to produce biochemical and bioenergy. Pretreatment of biomass can disrupt their complex structure, increasing conversion efficiency and product yield. Therefore, this review comprehensively discusses recent advances in different pretreatments (physical, chemical, physicochemical, and biological pretreatments) for lignocellulosic and algal biomass and their biorefining methods. Life cycle assessment (LCA) which enables the quantification of the environmental impact assessment of a biorefinery also be introduced. Biorefinery processes such as raw material acquisition, extraction, production, waste accumulation, and waste conversion are all monitored under this concept. Nevertheless, there still exist some techno-economic barriers during biorefinery and extensive research is still needed to develop cost-effective processes.

Recent advances in biogas production using Agro-Industrial Waste: A comprehensive review outlook of Techno-Economic analysis

Agrowaste sources can be utilized to produce biogas by anaerobic digestion reaction. Fossil fuels have damaged the environment, while the biogas rectifies the issues related to the environment and climate change problems. Techno-economic analysis of biogas production is followed by nutrient recycling, reducing the greenhouse gas level, biorefinery purpose, and global warming effect. In addition, biogas production is mediated by different metabolic reactions, the usage of different microorganisms, purification process, upgrading process and removal of CO₂ from the gas mixture techniques. This review focuses on pre-treatment, usage of waste, production methods and application besides summarizing recent advancements in biogas production. Economical, technical, environmental properties and factors affecting biogas production as well as the future perspective of bioenergy are highlighted in the review. Among all agro-industrial wastes, sugarcane straw produced 94% of the biogas. In the future, to overcome all the problems related to biogas production and modify the production process.

Recovering high value-added anthocyanins from blueberry pomace with ultrasound-assisted extraction

•

Food waste blueberry pomace offers a high potential to recover anthocyanins.

•

Ultrasonic-assisted extraction of anthocyanins was optimized by Box-Behnken design.

•

The optimal parameters of ultrasonic treatment were 40 °C and 400 W for 40 min.

•

Highly purified blueberry anthocyanins were obtained after SCX cation exchange.

•

Malvidin was the main anthocyanins in the purified fractions from blueberry pomace.

Food waste is a potential source to replace fresh materials for obtaining functional ingredients. Blueberry pomace contains considerable amounts of anthocyanins. In this study, we investigated ultrasonic-assisted extraction (UAE) of anthocyanins from blueberry pomace. We used a Box-Behnken design (BBD) to screen and optimize the important factors influencing yield. The optimum extraction conditions were a temperature of 40 °C, an ultrasonic power of 400 W and an extraction time of 40 min. The optimum yield was 108.23 mg/100 g DW. In addition, we used a cation column to separate anthocyanins, and optimized the chromatographic conditions of HPLC to analyze and identify the main anthocyanins. Thirteen anthocyanins were found in blueberry pomace, of which Malvidin-3-Galactoside (22.65 %) was the highest. These findings provide a theoretical basis and optimized process parameters for the recovery of high value-added anthocyanins from blueberry pomace with ultrasound-assisted extraction, thus facilitating the comprehensive utilization of blueberry pomace.

Leads and hurdles to sustainable microbial bioplastic production

Indiscriminate usage, disposal and recalcitrance of petroleum-based plastics have led to its accumulation leaving a negative impact on the environment. Bioplastics, particularly microbial bioplastics serve as an ecologically sustainable solution to nullify the negative impacts of plastics. Microbial production of biopolymers like Polyhydroxyalkanoates, Polyhydroxybutyrates and Polylactic acid using renewable feedstocks as well as industrial wastes have gained momentum in the recent years. The current study outlays types of bioplastics, their microbial sources and applications in various fields. Scientific evidence on bioplastics has suggested a unique range of applications such as industrial, agricultural and medical applications. Though diverse microorganisms such as Alcaligenes latus, Burkholderia sacchari, Micrococcus species, Lactobacillus pentosus, Bacillus sp., Pseudomonas sp., Klebsiella sp., Rhizobium sp., Enterobacter sp., Escherichia sp., Azototobacter sp., Protomonas sp., Cupriavidus sp., Halomonas sp., Saccharomyces sp., Kluyveromyces sp., and Ralstonia sp. are known to produce bioplastics, the industrial production of bioplastics is still challenging. Thus this paper also provides deep insights on the advancements made to maximise production of bioplastics using different approaches such as metabolic engineering, rDNA technologies and multitude of cultivation strategies. Finally, the constraints to microbial bioplastic production and the future directions of research are briefed. Hence the present review emphasizes on the importance of using bioplastics as a sustainable alternative to petroleum based plastic products to diminish environmental pollution.

A dark purple multifunctional ingredient from blueberry pomace enhanced with lactic acid bacteria for various applications

Nowadays, large quantities of berries are still being dumped or used for composting and animal feeding. The objective of this study was to customize a technological design for appropriate valorization of blueberry pomace into a shelf-life-stable, dark purple multifunctional ingredient, containing lactic acid bacteria (Lactobacillus casei), by freeze-drying. The main anthocyanins in blueberries freeze-dried inoculated pomace are malvidin 3-O-glucoside, peonidin 3-O-glucoside, and cyanidin 3-O-glucoside. A viable cells content of 4.75×10⁸ CFU/g DW was found after freeze-drying and the ability of the freeze-dried powder to inhibit the DPPH radical was 171.98 ± 1.73 mMol Trolox/g DW. The results obtained from CIElab analysis show a tendency to red and blue, characteristic of blueberry anthocyanins. The bioaccesibility of anthocyanins from blueberry powder was 37.8% and the probiotic survival rate after passing through the digestion process was 49.56%. The inhibitory potential of the obtained powder on α-amylase, pancreatic lipase, and α-glucosidase and tyrosinase was assessed. A significant antidiabetic potential of the powder was found, with IC50 values for α-amylase of 2.61 ± 0.24 mg/ml and for α-glucosidase of 1.37 ± 0.01 mg/ml, significantly lower when compared to corresponding drugs used in current practices. The powder also showed a significant potential to inhibit tyrosinase, supporting the hypothesis that the pomace resulting from juice and wine manufacturing may be successfully used to develop multifunctional ingredients with significant health benefits. PRACTICAL APPLICATION: Nowadays, food scientists and industry are seeking technological alternatives to obtain functional ingredients, due to the global interest in translating and applying scientific knowledge to address consumers' health issues. In our study, a freeze-drying customized design involving the use of the blueberry pomace, pectin, and Lactobacillus casei was applied to develop an ingredient with multiple functions. Besides a remarkable color, the powder showed good antioxidant activity, in vitro cells viability, and inhibitory activity against some metabolic syndrome-associated enzymes.

Microwave-Assisted Extraction of Polyphenols from Blackcurrant By-Products and Possible Uses of the Extracts in Active Packaging

The design of experiment (DoE) approach was used to optimize the extraction of polyphenols from blackcurrant by-products with microwave-assisted extraction and deionized water as a green solvent. Three factors (microwave power, extraction time, and solvent/matrix ratio) were evauated, and a central composite orthogonal design (CCO) was applied in order to reduce experimental runs. Empirical models relating the response and process parameters were developed. The validity of the models was tested using an analysis of variance (ANOVA). The optimal extraction conditions were found using the highest value of microwave power (780–800 W) and the lowest extraction time (60 min) and solvent/matrix ratio (10 m/g). Compared with conventional solvent extraction, the polyphenol yield increased by 25% after applying the optimized MAE process. The obtained extract was used to realize a sustainable active maltodextrin (Glucidex 2) pad using an electrospinning technique. The antimicrobial and antioxidant activities of the pads were tested on the post-harvest storage of raspberries. Two set of experiments were carried out. The recorded results showed that the pad had antimicrobial activity on the tested fruit samples and implied the possibility of using it to extend the shelf-life of the fruits.

Recovery of value-added products from biowaste: A review

This review provides an update on the state-of-the art technologies for the valorization of solid waste and its mechanism to generate various bio-products. The organic content of these wastes can be easily utilized by the microbes and produce value-added compounds. Microbial fermentation techniques can be utilized for developing waste biorefinery processes. The utilization of lignocellulosic and plastics wastes for the generation of carbon sources for microbial utilization after pre-processing steps will make the process a multi-product biorefinery. The C1 and C2 gases generated from different industries could also be utilized by various microbes, and this will help to control global warming. The review seeks to expand expertise about the potential application through several perspectives, factors influencing remediation, issues, and prospects.

Organic waste recycling for carbon smart circular bioeconomy and sustainable development: A review

The development of sustainable and low carbon impact processes for a suitable management of waste and by-products coming from different factors of the industrial value chain like agricultural, forestry and food processing industries. Implementing this will helps to avoid the negative environmental impact and global warming. The application of the circular bioeconomy (CB) and the circular economic models have been shown to be a great opportunity for facing the waste and by-products issues by bringing sustainable processing systems which allow to the value chains be more responsible and resilient. In addition, biorefinery approach coupled to CB context could offer different solution and insights to conquer the current challenges related to decrease the fossil fuel dependency as well as increase efficiency of resource recovery and processing cost of the industrial residues. It is worth to remark the important role that the biotechnological processes such as fermentative, digestive and enzymatic conversions play for an effective waste management and carbon neutrality.

Effects of different additives and aerobic composting factors on heavy metal bioavailability reduction and compost parameters: A meta-analysis

Additives are considered a promising approach to accelerate the composting process and alleviate the dissemination of pollutants to the environment. However, nearly all previous articles have focused on the impact of additive amounts on the reduction of HMs, which may not fully represent the main factor shaping HMs bioavailability status during composting. Simultaneously, previous reviews only explored the impacts, speciation, and toxicity mechanism of HMs during composting. Hence, a global-scale meta-analysis was conducted to investigate the response patterns of HMs bioavailability and compost parameters to different additives, composting duration, and composting factors (additive types, feedstock, bulking agents, and composting methods) by measuring the weighted mean values of the response ratio "[ln (RR)]" and size effect (%). The results revealed that additives significantly lessened HMs bioavailability by ≥ 40% in the final compost products than controls. The bioavailability decline rates were -40%, -60%, -57%, -55%, -42%, and -44% for Zn, Pb, Ni, Cu, Cr, and Cd. Simultaneously, additives significantly improved the total nitrogen (TN) (+16%), pH (+5%), and temperature (+5%), and decreased total organic carbon (TOC) (-17%), moisture content (MC) (-18%), and C/N ratio (-19%). Furthermore, we found that the prolongation of composting time significantly promoted the effect of additives on declining HMs bioavailability (p < 0.05). Nevertheless, increasing additive amounts revealed an insignificant impact on decreasing the HMs bioavailability (p > 0.05). Eventually, using zeolite as an additive, chicken manure as feedstock, sawdust as a bulking agent, and a reactor as composting method had the most significant reduction effect on HMs bioavailability (p < 0.05). The findings of this meta-analysis may contribute to the selection, modification, and application of additives and composting factors to manage the level of bioavailable HMs in the compost products.

Valorization of Berries' Agro-Industrial Waste in the Development of Biodegradable Pectin-Based Films for Fresh Salmon (Salmo salar) Shelf-Life Monitoring

The healthy properties of berries are known; however, red fruits are very perishable, generating large losses in production and marketing. Nonetheless, these wastes can be revalued and used. The main objective of this study was the development of biodegradable pectin films with berry agro-industrial waste extracts to monitor salmon shelf-life. The obtained extracts from blueberries, blackberries, and raspberries wastes were evaluated in terms of flavonols, phenols and anthocyanins contents, and antioxidant capacity. Then, pectin films with the extracts of different berries were developed and characterized. The results showed that the blueberry extract film was thicker (0.248 mm), darker (L* = 61.42), and opaquer (17.71%), while the highest density (1.477 g/cm3) was shown by the raspberry films. The results also showed that blueberries were the best for further application due to their composition in bioactive compounds, antioxidant capacity, and color change at different pHs. The salmon samples wrapped in blueberry films showed lower values of pH and deterioration of fish during storage compared to the control and pectin samples. This study contributes to the valorization of berries agro-industrial waste by the development of eco-friendly films that can be used in the future as intelligent food packaging materials contributing to the extension of food shelf-life as a sustainable packaging alternative.

Enhanced biogas production from food waste and activated sludge using advanced techniques - A review

Biogas generation using food waste anaerobic co-digestion with activated sludge provides a cleaner addressable system, an excellent solution to global challenges, the increasing energy demands, fuel charges, pollution and wastewater treatment. Regardless of the anaerobic digestate end product values, the technology lacks efficiency and process instability due to substrate irregularities. Process parameters and substrate composition, play a vital role in the efficiency and outcome of the system. Intrinsic biochar properties such as pore size, specific surface properties and cation exchange capacity make it an ideal additive that enriches microbial functions and enhances anaerobic digestion. The pretreatment and co-digestion of food waste and activated sludge are found to be significant for efficient biogas generation. The advantages, drawbacks, limitations, and technical improvements are covered extensively in the present review besides the recent advancement in the anaerobic digestion system.

Catalytic pyrolysis of lignocellulosic biomass for bio-oil production: A review

Catalytic pyrolysis has been widely explored for bio-oil production from lignocellulosic biomass owing to its high feasibility and large-scale production potential. The aim of this review was to summarize recent findings on bio-oil production through catalytic pyrolysis using lignocellulosic biomass as feedstock. Lignocellulosic biomass, structural components and fundamentals of biomass catalytic pyrolysis were explored and summarized. The current status of bio-oil yield and quality from catalytic fast pyrolysis was reviewed and presented in the current review. The potential effects of pyrolysis process parameters, including catalysts, pyrolysis conditions, reactor types and reaction modes on bio-oil production are also presented. Techno-economic analysis of full-scale commercialization of bio-oil production through the catalytic pyrolysis pathway was reviewed. Further, limitations associated with current practices and future prospects of catalytic pyrolysis for production of high-quality bio-oils were summarized. This review summarizes the process of bio-oil production from catalytic pyrolysis and provides a general scientific reference for further studies.

Current state of the art biotechnological strategies for conversion of watermelon wastes residues to biopolymers production: A review

Poly-3-hydroxyalkanoates (PHA) are biodegradable and compostable polyesters. This review is aimed to provide a unique approach that can help think tanks to frame strategies aiming for clean technology by utilizing cutting edge biotechnological advances to convert fruit and vegetable waste to biopolymer. A PHA manufacturing method based on watermelon waste residue that does not require extensive pretreatment provides a more environmentally friendly and sustainable approach that utilizes an agricultural waste stream. Incorporating fruit processing industry by-products and water, and other resource conservation methods would not only make the manufacturing of microbial bio-plastics like PHA more eco-friendly, but will also help our sector transition to a bioeconomy with circular product streams. The final and most critical element of this review is an in-depth examination of the several hazards inherent in PHA manufacturing.

A review on global perspectives of sustainable development in bioenergy generation

Over the last few decades, the globe has much relied on fossil fuels; however, environmental concerns forced the World to look at biofuel as an alternative for stable economic development. Biofuel also facilitates national energy security maintenance and reduces environmental complications. The present study is focused on an in-depth analysis of bioenergy policy measures undertaken by various federal agencies of different countries in order to shed light on the bottlenecks that impede biofuel's growth as a sustainable and alternative fuel. An in-depth assessment of feedstock utilization, blending targets, and policy assistance schemes have been thoroughly reviewed. In addition, the potential of commercial firms for the production of bioenergy is highlighted in order to grasp the current bioenergy market scenario better. Finally, the article is concluded with the viewpoints of the authors to address the standing issues of global bioenergy generation.

Advances in solid-state fermentation for bioconversion of agricultural wastes to value-added products: Opportunities and challenges

The increase in solid waste has become a common problem and causes environmental pollution worldwide. A green approach to valorise solid waste for sustainable development is required. Agricultural residues are considered suitable for conversion into profitable products through solid-state fermentation (SSF). Agricultural wastes have high organic content that is used as potential substrates to produce value-added products through SSF. The importance of process variables used in solid-phase fermentation is described. The applications of SSF developed products in the food industry as flavouring agents, acidifiers, preservatives and flavour enhancers. SSF produces secondary metabolites and essential enzymes. Wastes from agricultural residues are used as bioremediation agents, biofuels and biocontrol agents through microbial processing. In this review paper, the value addition of agricultural wastes by SSF through green processing is discussed with the current knowledge on the scenarios, sustainability opportunities and future directions of a circular economy for solid waste utilisation.

Recent trends and developments on integrated biochemical conversion process for valorization of dairy waste to value added bioproducts: A review

In this review article, discuss the many ways utilized by the dairy sector to treat pollutants, emphasizing their influence on the quality and efficiency with which contamination is removed. It focuses on biotechnology possibilities for valorizing dairy waste in particular. The findings revealed that dairy waste may be treated using physicochemical, biological, and biotechnological techniques. Notably, this article highlighted the possibility of dairy waste being used as a feedstock not only for the generation of biogas, bioethanol, biohydrogen, microbial fuel cells, lactic acid, and fumaric acid via microbial technology but also for the production of biooil and biochar by pyrolysis. In addition, this article critically evaluates the many treatment techniques available for recovering energy and materials from dairy waste, their combinations, and implementation prospects. Valorization of dairy waste streams presents an opportunity to extend the dairy industry's presence in the fermented functional beverage sector.

Methanogen and nitrifying genes dynamics in immersed membrane bioreactors during anaerobic co-digestion of different organic loading rates food waste

This work was aimed to evaluate the distinctive food waste (FW) organic loading rates (OLR) on methanogen and nitrifying genes dynamics and its correlation with identified relative abundance of bacterial dynamics during the anaerobic digestion. This experiment were carried out in the digesters at high OLR of food wastes at (4 to 8 g volatile solids/liter/day reactor R1) and (6 to 10 g volatile solids/liter/day reactor R2). The results shown that the relative abundance of mcrA, mcrB and mcrG genes were richest in the first day of both R1 and R2. In addition, the most of nitrifying genes were greater in after 34 days digestion in R2, while these genes did not show the specific regularity in R1. Finally, the correlation figure shows that Clostridium and Lactobacillus genera were significantly correlated with the different organic acids and methanogen and nitrifying genes dynamics.

Bioengineered biochar as smart candidate for resource recovery toward circular bio-economy: a review

Biochar's ability to mediate and facilitate microbial contamination degradation, as well as its carbon-sequestration potential, has sparked interest in recent years. The scope, possible advantages (economic and environmental), and future views are all evaluated in this review. We go over the many designed processes that are taking place and show why it is critical to look into biochar production for resource recovery and the role of bioengineered biochar in waste recycling. We concentrate on current breakthroughs in the fields of engineered biochar application techniques to systematically and sustainable technology. As a result, this paper describes the use of biomass for biochar production using various methods, as well as its use as an effective inclusion material to increase performance. The impact of biochar amendments on microbial colonisation, direct interspecies electron transfer, organic load minimization, and buffering maintenance is explored in detail. The majority of organic and inorganic (heavy metals) contaminants in the environment today are caused by human activities, such as mining and the use of chemical fertilizers and pesticides, which can be treated sustainably by using engineered biochar to promote the establishment of a sustainable engineered process by inducing the circular bioeconomy.