Biological and electrochemical valorisation of lignocellulosic wastes from pulp & paper industry to give new generation biodiesel and aromatic compounds

Technical 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 Protobind™ 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 production of glucose from giant reed and cardoon cellulose fraction and its fermentation to new generation oil by oleaginous yeasts

The 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

Cutaneotrichosporon oleaginosus: A Versatile Whole-Cell Biocatalyst for the Production of Single-Cell Oil from Agro-Industrial Wastes

Cutaneotrichosporon oleaginosus is an oleaginous yeast with several favourable qualities: It is fast growing, accumulates high amounts of lipids and has a very broad substrate spectrum. Its resistance to hydrolysis by-products makes it a promising biocatalyst for custom tailored microbial oils. C. oleaginosus can accumulate up to 60 wt.% of its biomass as lipids. This species is able to grow by using several compounds as a substrate, such as acetic acid, biodiesel-derived glycerol, N-acetylglucosamine, lignocellulosic hydrolysates, wastepaper and other agro-industrial wastes. This review is focused on state-of-the-art innovative and sustainable biorefinery schemes involving this promising yeast and second- and third-generation biomasses. Moreover, this review offers a comprehensive and updated summary of process strategies, biomass pretreatments and fermentation conditions for enhancing lipid production by C. oleaginosus as a whole-cell biocatalyst. Finally, an overview of the main industrial applications of single-cell oil is reported together with future perspectives

Challenges and opportunities in the catalytic synthesis of diphenolic acid and evaluation of its application potential

Diphenolic acid, or 4,4-bis(4-hydroxyphenyl)pentanoic acid, represents one of the potentially most interesting bio-products obtainable from the levulinic acid supply-chain. It represents a valuable candidate for the replacement of bisphenol A, which is strongly questioned for its toxicological issues. Diphenolic acid synthesis involves the condensation reaction between phenol and levulinic acid and requires the presence of a Brønsted acid as a catalyst. In this review, the state of the art related to the catalytic issues of its synthesis have been critically discussed, with particular attention to the heterogeneous systems, the reference benchmark being represented by the homogeneous acids. The main opportunities in the field of heterogeneous catalysis are deeply discussed, as well as the bottlenecks to be overcome to facilitate diphenolic acid production on an industrial scale. The regioselectivity of the reaction is a critical point because only the p,p-isomer is of industrial interest; thus, several strategies aiming at the improvement of the selectivity towards this isomer are considered. The future potential of adopting alkyl levulinates, instead of levulinic acid, as starting materials for the synthesis of new classes of biopolymers, such as new epoxy and phenolic resins and polycarbonates, is also briefly considered

Novel Challenges on the Catalytic Synthesis of 5-Hydroxymethylfurfural (HMF) from Real Feedstocks

The 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 HMFsynthesis 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

Isolation of Pure Lignin and Highly Digestible Cellulose from Defatted and Steam-Exploded Cynara cardunculus

In this work, a three-step approach to isolate the main components of lignocellulosic cardoon, lignin and cellulose, was investigated. The raw defatted biomass, Cynara cardunculus, after steam explosion was subjected to a mild organosolv treatment to extract soluble lignin (L1). Then, enzymatic hydrolysis was performed to achieve decomposition of the saccharidic portion into monosaccharides and isolate residual lignin (L2). The fractionation conditions were optimized to obtain a lignin as less degraded as possible and to maximize the yield of enzymatic hydrolysis. Furthermore, the effect of the use of aqueous ammonia as an extraction catalyst on both fractions was studied. Each fraction was characterized by advanced techniques, such as elemental analysis and 31P nuclear magnetic resonance (NMR), 13C–1H two-dimensional (2D)-NMR, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), and UV–vis spectroscopies for lignin and X-ray diffraction (XRD), Klason compositional analysis, elemental analysis, and ATR-FTIR spectroscopy for cellulose-rich fractions. The impact of the cellulose-rich fraction composition and crystallinity was also correlated to the efficiency of the hydrolysis step, performed using the enzymatic complex Cellic CTec3

Sustainable Valorisation and Efficient Downstream Processing of Giant Reed by High-Pressure Carbon Dioxide Pretreatment

This work investigated the catalytic high-pressure CO2 pretreatment of giant reed. CO2 is a renewable resource; its use does not generate chemical wastes and it can be easily removed and recycled. The effect of the addition of low concentrations of FeCl3 (0.16 wt%) and PEG 400 (1.0 wt%) on the hemicellulose hydrolysis to xylose and xylo-oligosaccharides (XOS) is reported for the first time. Under the optimised pretreatment conditions, the xylan conversion of 82 mol% and xylose and XOS yields of 43 and 20 mol% were achieved, respectively. The solid residues obtained from different pretreatments were used as the substrate for the enzymatic hydrolysis to give glucose. The total glucose yield achieved under the optimised two-step process was 67.8 mol% with respect to the glucan units in the biomass. The results demonstrated that PEG-assisted FeCl3-catalysed scCO(2) pretreatment can produce xylose- or XOS-rich hydrolysates and improve the enzymatic hydrolysis of biomass

Chemical and biological catalysis for the green production of valuable carotenoids and triglycerides from waste wheat bran

Chemical and biological catalysis for the green production of valuable carotenoids and triglycerides from waste wheat bra

From food waste to fine chemicals: hydrolysis of defatted wheat bran and sugars conversion to lipids and carotenoids by fermentation

From food waste to fine chemicals: hydrolysis of defatted wheat bran and sugars conversion to lipids and carotenoids by fermentatio

PRIN LEVANTE 2020: VALORIZZAZIONE DELL’ACIDO LEVULINICO ATTRAVERSO TECNOLOGIE INNOVATIVE

Il progetto LEVANTE si focalizza sullo sviluppo di nuovi processi catalitici volti alla valorizzazione dell’acido levulinico e dei suoi esteri verso tre classi di composti: i rispettivi chetali, l’acido difenolico, il γ-valerolattone e i successivi prodotti di riduzione. Il progetto LEVANTE sarà sviluppato in accordo con i principi della green chemistry e della sostenibilità dei processi produttivi, aprendo così la strada a tecnologie innovative per la completa valorizzazione di tale composto