1,721,025 research outputs found
Biological and electrochemical valorisation of lignocellulosic wastes from pulp & paper industry to give new generation biodiesel and aromatic compounds
Get PDFTechnical lignin and cellulosic wastepaper represent the main side-streams of the existing industrial-scale biorefineries and paper industry. The valorisation of these renewable and low- or negative-value feedstocks is a strategic approach to enhance the biorefinery and paper industry sustainability. Lignin represents a promising source of aromatic compounds, while cellulosic wastepaper is a high-quality source of sugars which can be converted into several added-value bioproducts, such as biofuels, biochemicals and biomaterials. In this perspective, in the present work, the electrochemical valorisation of lignin to give aromatics was performed [1], whereas in the case of wastepaper, a direct enzymatic hydrolysis was optimised to simultaneously produce glucose and xylose which were then fermented by oleaginous yeasts to produce new generation biodiesel [2]. In particular, the soda technical lignin ProtobindTM 1000 (P1000) was adopted as starting material. It is produced on an industrial scale by the company GreenValue (Switzerland), starting from a mix of wheat straw and sarkanda grass, after an alkaline extraction with sodium hydroxide.
In order to improve the lignin exploitation to added-value aromatic compounds, a mild chemical conversion route based on electrochemistry was investigated [1]. Under the optimal reaction conditions (NiOOH electrode, pH 14, lignin 20 g/L, 0.4 V), the electro-oxidative depolymerisation of lignin by electrolysis was performed in a divided cell. The main products were sinapic acid, vanillin, vanillic acid, and acetovanillone. The obtained preliminary results demonstrated the potential feasibility of this innovative electrochemical route for lignin valorisation for the production of bio-aromatic chemicals.
The wastepaper derived from the converting process for the production of tissue paper products by different local companies in Lucca (Italy). The waste cellulosic powder is produced in the converting section, where the paper coil is unrolled and the sheet is subjected to mechanical operations to give the final commercial product. This cellulosic waste is not suitable to be recycled within the same papermaking process. For this reason, it is typically recovered by aspiration and sent to the landfill. Regarding the exploitation of wastepaper, an innovative two-step process for the conversion of waste tissue paper to single cell oil (SCO) was optimised. SCO represents an outstanding alternative to both fossil sources and vegetable oils for the production of biodiesel. Hydrolysates containing glucose and xylose were produced by enzymatic hydrolysis of the untreated waste. Under the optimised reaction conditions (Cellic® CTec2 25 FPU/g glucan, 48 h, biomass loading 20 g/L), the yield of 95 mol% was reached for both glucose and xylose. The undetoxified hydrolysate was adopted as substrate for a batch-mode fermentation by the oleaginous yeast Lipomyces starkeyi. Lipid yield, lipid content for single cell, oil production and maximum oil productivity were 20.2 wt%, 37 wt%, 3.7 g/L and 2.0 g/L/d, respectively. This new generation oil, obtained from a negative value industrial waste, represents a promising platform chemical for the production of biodiesel, biosurfactants, animal feed and biobased plastics
Microwave-assisted FeCl3-catalysed hydrolysis of giant reed and cardoon cellulose followed by fermentation to single cell oil by Lipomyces starkeyi
Get PDFThis study investigated the microwave-assisted FeCl3-catalysed hydrolysis of giant reed (Arundo donax L.) and defatted cardoon (Cynara cardunculus L.) cellulose fractions to give glucose. Giant reed is a promising energy crops able to grow on marginal lands, while cardoon stalks are the crop residue in the production of vegetable oil. A preliminary acid pretreatment was adopted for giant reed, while steam-explosion pretreatment was performed on cardoon, both allowing a significant removal of xylan fractions. Under different reactions conditions the microwave-assisted FeCl3-catalysed hydrolysis converted the two pretreated feedstocks into glucose-rich hydrolysates which were employed as fermentation medium for the production of single cell oil (SCO) by the oleaginous yeast Lipomyces starkeyi DSM 70296. For giant reed, the low production of furanic compounds enabled the fermentation of undetoxified hydrolysates, while for cardoon the furfural removal was necessary before the fermentation step. After hydrolysis, for both hydrolysates the fermentation provided good lipid yields (~14 wt%) and oil content (~25 wt%). The SCO appears a valid candidate for the production of new generation biodiesel with good oxidative stability and cold flow properties. Moreover, it resulted very similar to palm and rapeseed oils, usually employed as a renewable source for the production of traditional biodiesel
Tailoring the porosity of chemically activated carbons derived from the HTC treatment of sewage sludge for the removal of pollutants from gaseous and aqueous phases
No full textThe management of sewage sludge is currently an open issue due to the large volume of waste to be treated and the necessity to avoid incineration or landfill disposal. Hydrothermal carbonization (HTC) has been recognized as a promising thermochemical technique to convert sewage sludge into value-added products. The hydrochar (HC) obtained can be suitable for environmental application as fuel, fertilizer, and sorbent. In this study, activated hydrochars (AHs) were prepared from sewage sludge through HTC followed by chemical activation with potassium hydroxide (KOH) and tested for the removal of pollutants in gaseous and aqueous environments, investigating carbon dioxide (CO2) and ciprofloxacin (CIP) adsorption capacity. The effects of activation temperature (550-750 °C) and KOH/HC impregnation ratio (1-3) on the produced AHs morphology and adsorption capacity were studied by Response Surface Methodology (RSM). The results of RSM analysis evidenced a maximum CO2 uptake of 71.47 mg/g for mild activation conditions (600-650 °C and KOH/HC = 1 ÷ 2), whereas the best CIP uptake of 628.61 mg/g was reached for the most severe conditions (750 °C, KOH/HC = 3). The prepared AHs were also applied for the removal of methylene blue (MB) from aqueous solutions, and the MB uptake results were used for estimating the specific surface area of AHs. High surface areas up to 1902.49 m2/g were obtained for the highest activation temperature and impregnation ratio investigated. Predictive models of CO2 and CIP uptake were developed by RSM analysis, and the optimum activation conditions for maximizing the adsorption performance together with high AH yield were identified: 586 °C and KOH/HC ratio = 1.34 for maximum yield (26.33 %) and CO2 uptake (67.31 mg/g); 715 °C and KOH/HC ratio = 1.78 for maximum yield (18.75 %) and CIP uptake (370.77 mg/g). The obtained results evidenced that chemical activation of previously HTC-treated sewage sludge is a promising way to convert waste into valuable low-cost adsorbents
Innovative green catalysts to produce second generation sugars from non-food crops as a versatile biorefinery platform
No full textNowadays, the transformation of lignocellulosic biomass into added-value products such as reducing sugars is attracting great attention. Pentose and hexose sugars are very important industrial intermediates because they represent a versatile platform for the synthesis of several valuable compounds through chemical or biotechnological approaches. The present study was focused on the valorization of two promising non-food crops, such as giant reeds (Arundo donax L.) and cardoon (Cynara cardunculus L.) through the employment of homogeneous and heterogeneous catalysts for the production of C5 and C6 rich hydrolyzates. All reactions were performed in a microwave reactor and in aqueous medium
Catalytic and biocatalytic cascade conversion of giant reed and cardoon residues to glucose, levulinic acid, and long-chain fatty acid methyl esters
No full textGiant reed was hydrolysed by the green salt FeCl3 under microwave irradiation. Differently, cardoon residues were pretreated by steam explosion and hydrolysed by the same catalyst. Each pretreatment showed efficient biomass fractionation, with xylan hydrolysis reaching 99 mol% for giant reed and 70 mol% for cardoon. Then, glucose yields of 55 and 30 mol% were obtained for giant reed and cardoon, respectively, under mild reaction conditions (34 min, 150 °C, biomass loading 9 wt%, FeCl3 2.7 wt%). Sugars-rich hydrolysates were fermented by the yeasts L. starkeyi and L. tetrasporus to produce triglycerides. L. starkeyi achieved a lipid yield of 13.5 wt% from giant reed hydrolysate and 14.2 wt% from cardoon hydrolysate. L. tetrasporus reached a lipid yield of 16.0 and 17.6 wt% from giant reed and cardoon hydrolysate, respectively. Moreover, both yeasts were able to convert cardoon hemicellulose into triglycerides, reaching at pH 5.5 a lipid yield of 13.9 wt% (L. starkeyi) and 19.4 wt% (L. tetrasporus). These oils were converted to long-chain fatty acids methyl esters. The final valorisation of unconverted glucan in solid residues resulted in the FeCl3-catalysed production of levulinic acid and formic acid to close the biorefinery cycle of both biomasses
Microwave-assisted FeCl3-catalysed production of glucose from giant reed and cardoon cellulose fraction and its fermentation to new generation oil by oleaginous yeasts
Get PDFThe replacement of fossil fuels and materials with biofuels and bioproducts is a crucial current global goal. Biorefining of lignocellulosic biomass generates pentose and hexose sugars which can be converted into several added-value bio-based compounds. Among biofuels, biodiesel is one of the most promising renewable energy sources since it does not require new technology and engines for its use. Traditional biodiesel is produced on the industrial scale starting from vegetable oils obtained from oleaginous crops, such as palm oil, rapeseed oil and sunflower oil. However, most of the oleaginous plant species are food crops, determining the ethical debate on the right use of these renewable resources and the competition between the energy industry and food chain. An innovative and promising solution is represented by single cell oil (SCO) produced from oleaginous yeasts. This new generation oil, if obtained from low or negative value industrial waste, represents a promising platform chemical for the production of biodiesel, biosurfactants, animal feed and biobased plastics [1]. This study investigated the microwave-assisted FeCl3-catalysed hydrolysis of giant reed (Arundo donax L.) and defatted cardoon (Cynara cardunculus L.) cellulose fractions to give glucose. Giant reed is a promising energy crops able to grow on marginal lands, while cardoon stalks are the crop residue in the production of vegetable oil. A preliminary acid pretreatment was adopted for giant reed [2], while steam-explosion pretreatment was performed on cardoon [3], both allowing a significant removal of xylan fractions. Under different reactions conditions, the microwave-assisted FeCl3-catalysed hydrolysis converted the two pretreated feedstocks into glucose-rich hydrolysates which were employed as fermentation medium for the production of SCO by the oleaginous yeast Lipomyces starkeyi DSM 70296. For giant reed, the low production of furanic compounds enabled the direct fermentation of undetoxified hydrolysates, while for cardoon the furfural removal was necessary before the fermentation step. After hydrolysis, for both hydrolysates the fermentation provided promising lipid yields (~14 wt%) and oil content (~25 wt%). Figure 1 shows the process layout of the implemented third-generation biorefinery scheme. The SCO appears a valid candidate for the production of new generation biodiesel with good oxidative stability and cold flow properties. Moreover, it resulted very similar to palm and rapeseed oils, usually employed as a renewable source for the production of traditional biodiesel
Physiological characterization of Kluyveromyces marxianus strains for the development of a microbial platform to obtain bioethanol from cheese whey permeate
No full textThe increasing interest in renewable feedstocks for biochemicals production includes the valorization of cheese whey (CW), a by-product of the dairy industry. CW contains a high concentration of lactose, accounting for most of its organic load, making it a major environmental pollutant if untreated. A valorization approach of CW is based on the separation of valuable proteins by ultrafiltration, and the obtainment of a lactose-rich cheese whey permeate (CWP). The conversion of lactose in CWP into bioethanol is considered a sustainable solution for the valorization of this waste. However, lactose is not metabolized by the yeast species Saccharomyces cerevisiae, namely the most industrially used microorganism, to produce bioethanol. Differently, the non-conventional yeast Kluyveromyces marxianus shows high growth rates on a broad range of industrially relevant substrates, including lactose. This study provides a comprehensive physiological characterization of three K. marxianus strains (DSM 5422, DSM 7239, and DSM 5572) to evaluate their potential for lactose hydrolysis and fermentation in order to produce advanced bioethanol from CWP. Microplate growth tests, β-galactosidase activity assays, and flask fermentations were carried out to identify optimal strains for efficient CWP valorization, advancing the applications of K. marxianus in industrial biotechnology. The optimal conditions for lactose utilization and ethanol production were identified as 130 g/L of lactose at 42 °C in semi-synthetic media (SSM). Even though strain DSM 7239 showed the highest β-galactosidase activity of 27.8 ± 0.9 U mg−1, strains DSM 5422 and 5572 were identified as the best performing strains at shake flask experiments in terms of ethanol yield on the substrate, with 0.48 ± 0.03 g/g and 0.50 ± 0.03 g/g, respectively, after 1 day of fermentation
Multivariate approach for the optimization of sucrose ethanolysis: Paving the way to the exploitation of sucrose-rich by-products
No full textThe depletion of fossil resources is making the synthesis of renewable compounds urgent. Ethyl levulinate (EL) represents a strategic compound within the biorefinery process, being a valuable intermediate, solvent and biofuel additive of renewable origin. The one-pot ethanolysis is the preferred route for its synthesis, but the proper optimization of the reaction conditions to maximize the EL yield and minimize the critical by-products formation, diethyl ether (DEE) and humins, is still a challenge. In this regard, the present work aims at the optimization of sucrose ethanolysis through the multivariate approach, adopting H2SO4 as catalyst and following the high gravity approach (10.5 wt% sucrose loading), which allows the obtaining of concentrated EL streams, increasing productivity and making downstream operations easier and cheaper. The optimization allowed a compromise between the highest EL yield and the lowest DEE production, thus simplifying EL purification and consuming less solvent that can be recycled in the following run. Under these conditions, the humins formation was also kept low and, for the first time, not only the solid humins were characterized, proving to be suitable as solid fuel turning into a co-product of the process, but also the chemical structure of the soluble ones was investigated. For the first time, a preliminary study regarding the ethanolysis of thick juice was also performed, thus opening the way to the employment of low-cost sucrose-rich feedstocks as substrate for the synthesis of EL. Thus, this work contributes to making the synthesis of a strategic renewable compound as EL more sustainable
New ruthenium(II) isocyanide catalysts for the transfer hydrogenation of ethyl levulinate to γ-valerolactone in C2-C6 alcohols
Get PDFTransfer hydrogenation (TH) processes are receiving great attention for biomass valorization and ruthenium(II) complexes are renowned TH catalysts both on laboratory and industrial scale. Only a few homogeneous catalytic precursors are available in the literature for the TH of ethyl levulinate (EL) to γ-valerolactone (GVL). Herein, starting from simple, commercially available isocyanides, two classes of air-stable ruthenium(II) complexes were synthesized and tested as catalytic precursors. First, an optimized preparation of Ru(II) p-cymene isocyanide complexes was developed. Then, the thermally induced p-cymene/DMSO substitution gave access to unprecedented ruthenium isocyanide-DMSO complexes. All the complexes were characterized and tested in TH of EL to GVL showing promising performances, adopting 2-propanol as hydrogen donor, a low catalyst (Ru) and co-catalyst (KOH) amount, working under microwave heating for 1 h at 150 °C. The most selective systems were also successfully tested with different biomass-derived alcohols, including 2-butanol. Finally, the recycling of the best catalyst was also investigated, thus improving the efficiency of the entire process
Novel Challenges on the Catalytic Synthesis of 5-Hydroxymethylfurfural (HMF) from Real Feedstocks
Get PDFThe depletion of fossil resources makes the transition towards renewable ones more urgent. For this purpose, the synthesis of strategic platform-chemicals, such as 5-hydroxymethylfurfural (HMF), represents a fundamental challenge for the development of a feasible bio-refinery. HMF perfectly deals with this necessity, because it can be obtained from the hexose fraction of biomass. Thanks to its high reactivity, it can be exploited for the synthesis of renewable monomers, solvents, and bio-fuels. Sustainable HMF synthesis requires the use of waste biomasses, rather than model compounds such as monosaccharides or polysaccharides, making its production more economically advantageous from an industrial perspective. However, the production of HMF from real feedstocks generally suffers from scarce selectivity, due to their complex chemical composition and HMF instability. On this basis, different strategies have been adopted to maximize the HMF yield. Under this perspective, the properties of the catalytic system, as well as the choice of a suitable solvent and the addition of an eventual pretreatment of the biomass, represent key aspects of the optimization of HMF synthesis. On this basis, the present review summarizes and critically discusses the most recent and attractive strategies for HMF production from real feedstocks, focusing on the smartest catalytic systems and the overall sustainability of the adopted reaction conditions
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