Review of methodological decisions in life cycle assessment (LCA) of biorefinery systems across feedstock categories.

The application of life cycle assessment (LCA) to biorefineries is a necessary step to estimate their environmental sustainability. This review explores contemporary LCA biorefinery studies, across different feedstock categories, to understand approaches in dealing with key methodological decisions which arise, including system boundaries, consequential or attributional approach, allocation, inventory data, land use changes, product end-of-life (EOL), biogenic carbon storage, impact assessment and use of uncertainty analysis. From an initial collection of 81 studies, 59 were included within the final analysis, comprising 22 studies which involved dedicated feedstocks, 34 which involved residue feedstocks (including by-products and wastes), and a further 3 studies which involved multiple feedstocks derived from both dedicated and secondary sources. Many studies do not provide a comprehensive LCA assessment, often lacking detail on decisions taken, omitting key parts of the value chain, using generic data without uncertainty analyses, or omitting important impact categories. Only 28% of studies included some level of primary data, while 39% of studies did not undertake an uncertainty or sensitivity analysis. Just 8% of studies included data related to dLUC with a further 8% including iLUC, and only 14% of studies considering product end of life within their scope. The authors recommend more transparency in biorefinery LCA, with justification of key methodological decisions. A full value-chain approach should be adopted, to fully assess burdens and opportunities for biogenic carbon storage. We also propose a more prospective approach, taking into account future use of renewable energy sources, and opportunities for increasing circularity within bio-based value chains.

Emerging trends in high-solids enzymatic saccharification of lignocellulosic feedstocks for developing an efficient and industrially deployable sugar platform.

For the techno-commercial success of any lignocellulosic biorefinery, the cost-effective production of fermentable sugars for the manufacturing of bio-based products is indispensable. High-solids enzymatic saccharification (HSES) is a straightforward approach to develop an industrially deployable sugar platform. Economic incentives such as reduced capital and operational expenditure along with environmental benefits in the form of reduced effluent discharge makes this strategy more lucrative for exploitation. However, HSES suffers from the drawback of non-linear and disproportionate sugar yields with increased substrate loadings. To overcome this bottleneck, researchers tend to perform HSES at high enzyme loadings. Nonetheless, the production costs of cellulases are one of the key contributors that impair the entire process economics. This review highlights the relentless efforts made globally to attain a high-titer of sugars and their fermentation products by performing efficient HSES at low cellulase loadings. In this context, technical innovations such as advancements in new pretreatment strategies, next-generation cellulase cocktails, additives, accessory enzymes, novel reactor concepts and enzyme recycling studies are especially showcased. This review further covers new insights, learnings and prospects in the area of lignocellulosic bioprocessing.

Recent progress in the microbial production of xylonic acid.

Interest in the production of renewable chemicals from biomass has increased in the past years. Among these chemicals, carboxylic acids represent a significant part of the most desirable bio-based products. Xylonic acid is a five-carbon sugar-acid obtained from xylose oxidation that can be used in several industrial applications, including food, pharmaceutical, and construction industries. So far, the production of xylonic acid has not yet been available at an industrial scale; however, several microbial bio-based production processes are under development. This review summarizes the recent advances in pathway characterization, genetic engineering, and fermentative strategies to improve xylonic acid production by microorganisms from xylose or lignocellulosic hydrolysates. In addition, the strengths of the available microbial strains and processes and the major requirements for achieving biotechnological production of xylonic acid at a commercial scale are discussed. Efficient native and engineered microbial strains have been reported. Xylonic acid titers as high as 586 and 171 g L-1 were obtained from bacterial and yeast strains, respectively, in a laboratory medium. Furthermore, relevant academic and industrial players associated with xylonic acid production will be presented.

Bio-products from algae-based biorefinery on wastewater: A review.

Increasing resource demand, predicted fossil resources shortage in the near future, and environmental concerns due to the production of greenhouse gas carbon dioxide have motivated the search for alternative 'circular' pathways. Among many options, microalgae have been recently 'revised' as one of the most promising due to their high growth rate (with low land use and without competing with food crops), high tolerance to nutrients and salts stresses and their variability in biochemical composition, in so allowing the supply of a plethora of possible bio-based products such as animal feeds, chemicals and biofuels. The recent raising popularity of Circular Bio-Economy (CBE) further prompted investment in microalgae, especially in combination with wastewater treatment, under the twofold aim of allowing the production of a wide range of bio-based products while bioremediating wastewater. With the aim of discussing the potential bio-products that may be gained from microalgae grown on urban wastewater, this paper presents an overview on microalgae production with particular emphasis on the main microalgae species suitable for growth on wastewater and the obtainable bio-based products from them. By selecting and reviewing 76 articles published in Scopus between 1992 and 2020, a number of interesting aspects, including the selection of algal species suitable for growing on urban wastewater, wastewater pretreatment and algal-bacterial cooperation, were carefully reviewed and discussed in this work. In this review, particular emphasis is placed on understanding of the main mechanisms driving formation of microalgal products (such as biofuels, biogas, etc.) and how they are affected by different environmental factors in selected species. Lastly, the quantitative information gathered from the articles were used to estimate the potential benefits gained from microalgae grown on urban wastewater in Campania Region, a region sometimes criticized for poor wastewater management.

Removal of Petroleum Contaminants Through Bioremediation with Integrated Concepts of Resource Recovery: A Review.

There is an upsurge in industrial production to meet the rising demands of the rapidly growing population globally. The enormous energy demand of the growing economies still depends upon petroleum. It has also resulted in environmental pollution due to the release of petroleum origin pollutants. Soil and aquifers, especially in the direct impact zones of petroleum refineries, are the worst hit. The integrated concept of bioremediation and resource recovery offers a sustainable solution to mitigate environmental pollution. It involves biodegradation, a benign utilization of toxic wastes, and the recycling of natural resources. Bioremediation is considered an integral contributor to the emerging concepts of bio-economy and sustainable development goals. This review article aims to provide an updated overview of bioremediation involving petroleum-based contaminants. Microbial degradation is discussed as a promising strategy for petroleum refinery effluent and sludge treatment. The review also provides an insight into resource reuse and recovery as a holistic approach towards sustainable refinery waste treatment. Furthermore, the integrated technologies that deserve in-depth exploration for future study in the refinery sector are highlighted in the present study.

Isolation of xylose-assimilating yeasts and optimization of xylitol production by a new Meyerozyma guilliermondii strain.

Production of xylitol from lignocellulosic biomass is of interest to modern biorefineries, because this biomass should be processed into a spectrum of chemicals (bio-based products) and not only energy. The isolation of new yeast strains capable of efficiently converting xylose into xylitol and withstanding inhibitors released from biomass hydrolysis can contribute to making its production feasible in biorefineries. Forty-three out of 128 yeast strains isolated from the gut of Passalidae beetles were capable of assimilating xylose as the sole carbon source. Meyerozyma guilliermondii UFV-1 was selected due to its ability to grow and ferment D-xylose in a synthetic medium. This yeast assimilated the broad range of sugars present in lignocellulosic biomass hydrolysates, such as xylose, raffinose, cellobiose, rhamnose, arabinose, and glucose. Its optimum growth conditions were pH 8.0 and a temperature of 30 °C. In concentrations of 0.07 mol/L acetic acid, 0.05 mol/L 5-hydroximethylfurfural, and 0.04 mol/L furfural, M. guilliermondii UFV-1 did not grow. Maximum xylitol production in aerobiosis and hypoxia were 51.88 and 27.73 g/L, respectively. Under aerobic condition, xylose concentration and agitation rate were the factors which were statistically significant, while only the agitation rate was significant in hypoxia. We fitted a response surface (RS) that estimated the best agitation rate (113.33 rpm) and xylose concentration (90 g/L) for maximum xylitol production in aerobiosis. Therefore, M. guilliermondii UFV-1 displays potential for being used for xylitol production in biorefineries.

Kiwi fruit residues from industry processing: study for a maximum phenolic recovery yield.

A response surface methodology was used to study the conditions for a maximum recovery of phenolics from processing kiwi fruit residues. Ethanolic extracts were prepared with different conditions of pH (2, 5, 10), temperature (30, 50 and 70 ºC) and time (10, 20, 30 min). Total phenolics, total flavonoids content and antioxidant activities by 2,2-diphenyl-1-picrylhydrazyl scavenging capacity and ferric reducing antioxidant power were determined. Samples from optimal extraction condition were injected HPLC-DAD system to access the phenolic profile and content. The best extraction conditions were pH solvent of 2, 70 ºC of temperature and 20 min of extraction. Ten phenolics were identified: caffeic acid and its derivatives, chlorogenic acid and ferulic acid, (+)-catechin, (-)-epicatechin), rutin and quercitrin. These phenolics often reported as having important antioxidant, anti-inflammatory, antiaging and anticancer activities, turn this residues and excellent source of bioactive compounds to be used in agro-food, cosmetics or phytochemical industries.

Biomass from microalgae: the potential of domestication towards sustainable biofactories.

Interest in bulk biomass from microalgae, for the extraction of high-value nutraceuticals, bio-products, animal feed and as a source of renewable fuels, is high. Advantages of microalgal vs. plant biomass production include higher yield, use of non-arable land, recovery of nutrients from wastewater, efficient carbon capture and faster development of new domesticated strains. Moreover, adaptation to a wide range of environmental conditions evolved a great genetic diversity within this polyphyletic group, making microalgae a rich source of interesting and useful metabolites. Microalgae have the potential to satisfy many global demands; however, realization of this potential requires a decrease of the current production costs. Average productivity of the most common industrial strains is far lower than maximal theoretical estimations, suggesting that identification of factors limiting biomass yield and removing bottlenecks are pivotal in domestication strategies aimed to make algal-derived bio-products profitable on the industrial scale. In particular, the light-to-biomass conversion efficiency represents a major constraint to finally fill the gap between theoretical and industrial productivity. In this respect, recent results suggest that significant yield enhancement is feasible. Full realization of this potential requires further advances in cultivation techniques, together with genetic manipulation of both algal physiology and metabolic networks, to maximize the efficiency with which solar energy is converted into biomass and bio-products. In this review, we draft the molecular events of photosynthesis which regulate the conversion of light into biomass, and discuss how these can be targeted to enhance productivity through mutagenesis, strain selection or genetic engineering. We outline major successes reached, and promising strategies to achieving significant contributions to future microalgae-based biotechnology.

Fungal biodiversity to biotechnology.

Fungal habitats include soil, water, and extreme environments. With around 100,000 fungus species already described, it is estimated that 5.1 million fungus species exist on our planet, making fungi one of the largest and most diverse kingdoms of eukaryotes. Fungi show remarkable metabolic features due to a sophisticated genomic network and are important for the production of biotechnological compounds that greatly impact our society in many ways. In this review, we present the current state of knowledge on fungal biodiversity, with special emphasis on filamentous fungi and the most recent discoveries in the field of identification and production of biotechnological compounds. More than 250 fungus species have been studied to produce these biotechnological compounds. This review focuses on three of the branches generally accepted in biotechnological applications, which have been identified by a color code: red, green, and white for pharmaceutical, agricultural, and industrial biotechnology, respectively. We also discuss future prospects for the use of filamentous fungi in biotechnology application.

Growth inhibition of S. cerevisiae, B. subtilis, and E. coli by lignocellulosic and fermentation products.

This paper describes the effect of several inhibiting components on three potential hosts for the bio-based production of methyl propionate, namely, wild-type Escherichia coli and Bacillus subtilis, and evolved Saccharomyces cerevisiae IMS0351. The inhibition by the lignocellulose-derived products 5-hydroxymethyl-2-furaldehyde, vanillin, and syringaldehyde and the fermentation products 2-butanol, 2-butanone, methyl propionate, and ethyl acetate has been assessed for these strains in defined medium. Multiple screenings were performed using small-scale cultures in both shake flasks and microtiter plates. Technical drawbacks revealed the limited applicability of the latter in this study. The microbial growth was characterized by means of a lag-time model, and the inhibitory thresholds were determined using product-inhibition models. The lignocellulose-derived products were found to be highly inhibitory, and none of the strains could grow in the presence of 2.0 g L-1 of product. From the fermentation products tested, methyl propionate had the most severe impact resulting in complete inhibition of all the strains when exposed to concentrations in the range of 12-18 g L-1. In general, S. cerevisiae and B. subtilis were comparatively more tolerant than E. coli to all the fermentation products, despite E. coli's lower sensitivity towards vanillin. The results suggest that, overall, the strains investigated have good potential to be engineered and further established as hosts for the bio-based production of methyl esters.

Recirculation: A New Concept to Drive Innovation in Sustainable Product Design for Bio-Based Products.

Bio-based products are made from renewable materials, offering a promising basis for the production of sustainable chemicals, materials, and more complex articles. However, biomass is not a limitless resource or one without environmental and social impacts. Therefore, while it is important to use biomass and grow a bio-based economy, displacing the unsustainable petroleum basis of energy and chemical production, any resource must be used effectively to reduce waste. Standards have been developed to support the bio-based product market in order to achieve this aim. However, the design of bio-based products has not received the same level of attention. Reported here are the first steps towards the development of a framework of understanding which connects product design to resource efficiency. Research and development scientists and engineers are encouraged to think beyond simple functionality and associate value to the potential of materials in their primary use and beyond.

Integrated sustainability assessment of wood building products: The case of larch and chestnut cascading systems in Northern Italy.

Wood is increasingly being appreciated in construction due to its valuable environmental attributes. This paper explores the environmental and market performance of two wood supply chains in Northern Italy. Larch and chestnut wood are extracted and processed to obtain beams, planks, MDF panels and energy. LCA is performed to evaluate the environmental impacts of 1m3 of extracted wood through a cradle-to-gate approach. Then, a biogenic carbon analysis is carried out using the EN 16449:2014 standard including a comparison of different end-of-life treatments. Also, OSB is proposed as an alternative path for wood chips and contrasted to the current energy scenario. Moreover, solid wood beams and planks are compared with engineered wood products (EWPs). Lastly, a market analysis is conducted to assess the market trends of the different wood products studied. The LCA shows similar results for both wood species across most impact categories, with slightly higher values for the chestnut system. Most impacts are related to the production of MDF boards and the energy valorization of wood chips. Biogenic carbon analysis shows a negative balance of emissions with -314 and -205 kg of CO2 eq for larch and chestnut, respectively. It also suggests that OSB manufacturing can be a valuable alternative to the energy use of wood chips and that the end-of-life treatment with better results is recycling. The comparison of beams and planks with engineered wood products supports that solid wood poses a better environmental alternative in similar applications. Market analysis shows stagnation in the apparent consumption of wood products in the European market and a slight growth in the Italian one between 2018 and 2022. Overall, the systems studied suggest that the potential environmental benefits of using wood in construction are not being matched by current market trends.

Photobioreactors for building integration: A overview of designs and architectural potential.

The global community faces critical energy and environmental challenges, necessitating innovative solutions to ensure a sustainable future.In response to these challenges, this paper explores the potential of integrating microalgal biotechnology with renewable energy systems within buildings. This innovative approach could transform architecture into a "bio-factory" capable of producing food, energy, and other valuable products.The success of this concept hinges on developing highly efficient photobioreactors specifically designed for building integration. Optimizing these systems requires careful consideration of design parameters, growth rate models, and factors influencing performance within diverse urban environments.Furthermore, integrating these systems must prioritize productivity and aesthetics to promote urban self-sufficiency and a sustainable built environment. By utilizing microalgae and renewable energy sources, building-integrated photobioreactors offer a promising solution for reducing energy consumption and carbon footprints in modern buildings.

[Biomanufacturing driven by engineered organisms (2022)].

This article summarizes the reviews and original research papers published in Chinese Journaol of Biotechnology in the area of biomanufacturing driven by engineered organisms in the year of 2022. The enabling technologies including DNA sequencing, DNA synthesis, and DNA editing as well as regulation of gene expression and in silico cell modeling were highlighted. This was followed by discussing the biomanufacturing of biocatalytics products, amino acids and its derivatives, organic acids, natural products, antibiotics and active peptides, functional polysaccharides, and functional proteins. Lastly, the technologies for utilizing C1 compounds and biomass as well as synthetic microbial consortia were discussed. The aim of this article was to help the readers to gain insights into this rapidly developing field from the journal point of view.

[Plant biomass degradation by filamentous fungi and production of renewable chemicals: a review].

Plant biomass represents a vast resource of carbon. In China, it is estimated that 1 billion tons of biomass is available each year. The conversion of these biomass resources into bioethanol or other bio-based chemicals, if fully commercialized, may reduce at least 200 million tons of crude oil import. Therefore, bioethanol and bulk chemicals are the core components of the biomanufacturing using plant biomass as carbon sources. Since the foundation of Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences (TIB, CAS), we have proposed a strategy of "two replacements and one upgrade". Utilizing renewable carbon resources instead of non-renewable petrochemical resources to produce bulk chemicals is included in our strategy. It is a long-term effort for TIB to develop plant biomass biomanufacturing to produce renewable chemicals. Continuous and systematic research was carried out in these two fields, and significant progress has been made in the past 10 years since the foundation of TIB. Here we review the progress of TIB in this field, mainly focusing on fungal system, including the mechanism of cellulose degradation by filamentous fungi and the strategy of consolidated bioprocessing of biomass. Based on this, malic acid, fuel ethanol and other bulk chemicals were produced through one-step conversion of biomass. Besides, the commercial processes for production of bulk chemicals such as succinic and lactic acid from renewable carbon resources, which were developed by TIB, were also be discussed. These examples clearly demonstrated that bulk chemicals can be obtained from biomass instead of from petroleum. Research on plant biomass biotransformation and renewable chemicals production in TIB has provided an alternative route for the development of low-carbon bioeconomy in China, and will contribute to the goal of carbon neutralization of China.

The Potential of Brewer's Spent Grain in the Circular Bioeconomy: State of the Art and Future Perspectives.

Brewer's spent grain (BSG) accounts for approximately 85% of the total mass of solid by-products in the brewing industry and represents an important secondary raw material of future biorefineries. Currently, the main application of BSG is limited to the feed and food industry. There is a strong need to develop sustainable pretreatment and fractionation processes to obtain BSG hydrolysates that enable efficient biotransformation into biofuels, biomaterials, or biochemicals. This paper aims to provide a comprehensive insight into the availability of BSG, chemical properties, and current and potential applications juxtaposed with the existing and emerging markets of the pyramid of bio-based products in the context of sustainable and circular bioeconomy. An economic evaluation of BSG for the production of highly valuable products is presented in the context of sustainable and circular bioeconomy targeting the market of Central and Eastern European countries (BIOEAST region).

Integrated biorefinery development using winery waste streams for the production of bacterial cellulose, succinic acid and value-added fractions.

An integrated biorefinery has been developed using winery wastes (grape pomace-GP, stalks-GS, wine lees-WL). Bacterial cellulose was produced from GP extracted free sugars. Grape-seed oil and polyphenols were extracted from GP. Experimental design was employed to optimize lignin removal (50.8%) from mixtures of remaining GP solids and GS via NaOH (1.19% w/v) treatment at 70°C for 30 min. Delignification liquid contained condensed tannins with 76% Stiasny number. Enzymatic hydrolysis produced a sugar-rich hydrolysate (40.2 g/L sugars). Ethanol, antioxidants, tartaric acid and nutrient-rich hydrolysate were produced from WL. The crude hydrolysates were used in fed-batch Actinobacillus succinogenes cultures for 37.2 g/L succinic acid production. The biorefinery produces 42.65 g bacterial cellulose, 24.3 g oil, 40.3 g phenolic-rich extract with 1.41 Antioxidant Activity Index, 80.2 g ethanol, 624.8 g crude tannin extract, 20.03 g tartaric acid and 157.8 g succinic acid from 1 kg of each waste stream.

Recovery of sugars and amino acids from brewers' spent grains using subcritical water hydrolysis in a single and two sequential semi-continuous flow-through reactors.

This study evaluated the subcritical water hydrolysis (SWH) of brewer's spent grains (BSG) to obtain sugars and amino acids. The experimental conditions investigated the hydrolysis of BSG in a single flow-through reactor and in two sequential reactors operated in semi-continuous mode. The hydrolysis experiments were carried out for 120 min at 15 MPa, 5 mL water min-1, at different temperatures (80 - 180 °C) and using an S/F of 20 and 10 g solvent g-1 BSG, for the single and two sequential reactors, respectively. The highest monosaccharide yields were obtained at 180 °C in a single reactor (47.76 mg g-1 carbohydrates). With these operational conditions, the hydrolysate presented xylose (0.477 mg mL-1) and arabinose (1.039 mg mL-1) as main sugars, while low contents of furfural (310.7 µg mL-1), 5-hydroxymethylfurfural (<1 mg L-1), and organic acids (0.343 mg mL-1) were obtained. The yield of proteins at 180 °C in a process with a single reactor was 43.62 mg amino acids g-1 proteins, where tryptophan (215.55 µg mL-1), aspartic acid (123.35 µg mL-1), valine (64.35 µg mL-1), lysine (16.55 µg mL-1), and glycine (16.1 µg mL-1) were the main amino acids recovered in the hydrolysate. In conclusion, SWH pretreatment is a promising technology to recover bio-based compounds from BSG; however, further studies are still needed to increase the yield of bioproducts from lignocellulosic biomass to explore two sequential reactors.

Advances and opportunities in integrating economic and environmental performance of renewable products.

There is a growing global need to transition from a fossil-based to a bio-based economy to produce fuels, chemicals, food, and materials. In the specific context of industrial biotechnology, a successful transition toward a sustainable development requires not only steering investment toward a bioeconomy, but also responsibly introducing bio-based products with lower footprints and competitive market prices. A comprehensive sustainability assessment framework applied along various research stages to guide bio-based product development is urgently needed but currently missing. To support holistic approaches to strengthen the global bioeconomy, the present study discusses methodologies and provides perspectives on the successful integration of economic and environmental performance aspects to guide product innovation in biotechnology. Efforts on quantifying the economic and environmental performance of bio-based products are analyzed to highlight recent trends, challenges, and opportunities. We critically analyze methods to integrate Techno-Economic Assessment (TEA) and Life Cycle Assessment (LCA) as example tools that can be used to broaden the scope of assessing biotechnology systems performance. We highlight the lack of social assessment aspects in existing frameworks. Data need for jointly applying TEA and LCA of succinic acid as example commodity chemical are assessed at various Technology readiness levels (TRLs) to illustrate the relevance of the level of integration and show the benefits of the use of combined assessments. The analysis confirms that the implementation of integrated TEA and LCA at lower TRLs will provide more freedom to improve bio-based product's sustainability performance. Consequently, optimizing the system across TRLs will guide sustainability-driven innovation in new biotechnologies transforming renewable feedstock into valuable bio-based products.

From hemp grown on carbon-vulnerable lands to long-lasting bio-based products: Uncovering trade-offs between overall environmental impacts, sequestration in soil, and dynamic influences on global temperature.

In this study, the potential of carbon storage in soil combined with mitigation via bio-based products is investigated for the case of 100 years of hemp cultivation on carbon-vulnerable land (CV-lands) in France. The originality of this study lies in the coupling of soil organic carbon (SOC) simulations (over 100 years of hemp cultivation) with consequential life cycle assessment (LCA) to investigate the mitigation potential of different environmental impacts, and the coupling with dynamic LCA to investigate the long-term effects on global warming. When hemp stems (straw) are left on the ground, SOC increases of 25.8 t ha-1 are observed over 100 years. However, the greenhouse gas (GHG) emissions that result from diverting the initial land use to hemp cultivation cannot be compensated for and, therefore, this scenario cannot mitigate global warming or most other impacts. Two long-lasting product scenarios were studied: insulation boards in buildings and car panels, both involving the production of hemp concrete as co-product. Our study shows that, even though no additional long-term carbon sequestration in soil could be achieved, both scenarios ensured a long-term climate benefit well beyond 2100, mostly because of carbon sequestered in the hemp-based products but also as a result of avoided fossil-based products. Uncertainty analyses reveal that the yield is the most influential parameter, inducing significant uncertainties in all scenarios and most impact categories. According to the overall results obtained, the car panel scenario is the most promising pathway with the lowest environmental impacts and the highest potential for long-term global warming mitigation; this is in part due to the reduction of fuel consumption during the use phase.