Green and sustainable manufacture of chemicals from biomass: state of the art

A catalytic lignocellulose biorefinery process is presented, valorizing both polysaccharide and lignin components into a handful of chemicals. To that end, birch sawdust is efficiently delignified through simultaneous solvolysis and catalytic hydrogenolysis in the presence of a Ru on carbon catalyst (Ru/C) in methanol under a H2 atmosphere at elevated temperature, resulting in a carbohydrate pulp and a lignin oil. The lignin oil yields above 50% of phenolic monomers (mainly 4-n-propylguaiacol and 4-n-propylsyringol) and about 20% of a set of phenolic dimers, relative to the original lignin content, next to phenolic oligomers. The structural features of the lignin monomers, dimers and oligomers were identified by a combination of GC/MS, GPC and 2D HSQC NMR techniques, showing interesting functionalities for forthcoming polymer applications. The effect of several key parameters like temperature, reaction time, wood particle size, reactor loading, catalyst reusability and the influence of solvent and gas were examined in view of the phenolic product yield, the degree of delignification and the sugar retention as a first assessment of the techno-economic feasibility of this biorefinery process. The separated carbohydrate pulp contains up to 92% of the initial polysaccharides, with a nearly quantitative retention of cellulose. Pulp valorization was demonstrated by its chemocatalytic conversion to sugar polyols, showing the multiple use of Ru/C, initially applied in the hydrogenolysis process. Various lignocellulosic substrates, including genetically modified lines of Arabidopsis thaliana, were finally processed in the hydrogenolytic biorefinery, indicating lignocellulose rich in syringyl-type lignin, as found in hardwoods, as the ideal feedstock for the production of chemicals.

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Reductive lignocellulose fractionation into soluble lignin-derived phenolic monomers and dimers and processable carbohydrate pulps

Bioethanol is one of the most promising and eco-friendly alternatives to fossil fuels, which is produced from renewable sources. Although almost all the current fuel ethanol is generated from edible sources (sugars and starch), lignocellulosic biomass (LCB) has drawn much attention in recent times. However, the conversion efficiency as well as ethanol yield of the biomass differs greatly with respect to the source and nature of LCB, primarily due to the variation in lignocellulosic content. Two major polysaccharides in LCB, namely, cellulose and hemicellulose firmly link to lignin and form a complex lignocellulosic network, which is highly robust and recalcitrant to depolymerization. For this reason, generation of ethanol from LCB requires a complicated conversion process that has made it commercially non-competitive. As attempts to exploit LCBs into commercial ethanol production, recent research efforts have been devoted to the techno-economic improvements of the overall conversion process, in addition to screen out promising feedstocks. This review paper presents an overview on the diversity of biomass, technological approaches and microbial contribution to the conversion of LCB into ethanol.

Fuel ethanol production from lignocellulosic biomass: an overview on feedstocks and technological approaches.

Bioethanol is an attractive biofuel having potential for energy security and environmental safety over fossil fuels. To date, numerous biomass resources have been investigated for bioethanol production, which can broadly be classified into sugars, starch and lignocellulosic biomass. However, conversion of biomass into ethanol varies considerably depending on the nature of feedstock, primarily due to the variation in biochemical composition, and so, only a few feedstocks have been exploited commercially. In recent years, the conversion process of biomass has been improved significantly, even though most of these achievements are yet to be implemented in commercial facility. All the major steps in a typical conversion process, particularly fermentation of sugars that is the common step for all biomass, are greatly influenced by microorganisms. A traditional yeast, Saccharomyces cerevisiae, and a bacterial species, Zymomonas mobilis, are widely used in the ethanol fermentation technology. Many factors affect ethanol production process, and the final yield is directly associated with the optimum conditions of these attributes. This review paper presents an overview on the first and second generation bioethanol production with a particular attention to the potential of various biomass sources, technological approaches, role of microorganisms and factors affecting ethanol production process.

Bioethanol production from renewable sources: Current perspectives and technological progress

A review on the pretreatment of lignocellulose for high-value chemicals

Lignin materials are abundant and among the most important potential sources for biofuel production. Development of an efficient lignin degradation process has considerable potential for the production of a variety of chemicals, including bioethanol. However, lignin degradation using current methods is inefficient. Given their immense environmental adaptability and biochemical versatility, bacterial could be used as a valuable tool for the rapid degradation of lignin. Kraft lignin (KL) is a polymer by-product of the pulp and paper industry resulting from alkaline sulfide treatment of lignocellulose, and it has been widely used for lignin-related studies. Beta-proteobacterium Cupriavidus basilensis B-8 isolated from erosive bamboo slips displayed substantial KL degradation capability. With initial concentrations of 0.5–6 g L-1, at least 31.3% KL could be degraded in 7 days. The maximum degradation rate was 44.4% at the initial concentration of 2 g L-1. The optimum pH and temperature for KL degradation were 7.0 and 30°C, respectively. Manganese peroxidase (MnP) and laccase (Lac) demonstrated their greatest level of activity, 1685.3 U L-1 and 815.6 U L-1, at the third and fourth days, respectively. Many small molecule intermediates were formed during the process of KL degradation, as determined using GC-MS analysis. In order to perform metabolic reconstruction of lignin degradation in this bacterium, a draft genome sequence for C. basilensis B-8 was generated. Genomic analysis focused on the catabolic potential of this bacterium against several lignin-derived compounds. These analyses together with sequence comparisons predicted the existence of three major metabolic pathways: β-ketoadipate, phenol degradation, and gentisate pathways. These results confirmed the capability of C. basilensis B-8 to promote KL degradation. Whole genomic sequencing and systematic analysis of the C. basilensis B-8 genome identified degradation steps and intermediates from this bacterial-mediated KL degradation method. Our findings provide a theoretical basis for research into the mechanisms of lignin degradation as well as a practical basis for biofuel production using lignin materials.

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Characterization and genomic analysis of kraft lignin biodegradation by the beta-proteobacterium Cupriavidus basilensis B-8

Kraft lignin biodegradation by Novosphingobium sp. B-7 and analysis of the degradation process.

A newly isolated bacterium was screened out for its survival on medium with 6 000 mg/L kraft lignin as the sole carbon source and energy, and identified as Pandoraea sp. by 16S rRNA gene sequence analysis. The biodegradation experiment was carried out in mineral salt medium, containing 5 000 mg/L kraft lignin as only carbon and energy at pH 8.0 and 30 °C. Under these conditions, significant reduction in color and lignin content by the strain was observed after incubation for 5 d. The strain attains maximum reduction capability in color (44.6%) and lignin content (39.9%) within 5 d of incubation, and reduced chemical oxygen demand(COD) from initial concentration 7 399 to 3 980 mg/L at maximum reduction level of 46.2% on the 4th day. The total ion chromatograph (TIC) of compounds presented in the chloroform extract of control and bacterial treated samples shows the formation of several lignin-related aromatic compounds including some small molecular lignin fragments, indicating a strong destruction in the lignin structure.

Characterization of a newly isolated Bacterium Pandoraea sp. B-6 capable of degrading kraft lignin

As a major component of lignin and abundantly existing in softwood and hardwood, ferulic acid has been used as a lignin-related compound for lignin biodegradation study. Biodegradation of ferulic acid by Cupriavidus sp. B-8, a newly isolated strain, was studied. This strain is able to utilize a wide range of lignin-related aromatic compounds as the sole carbon and energy source, including guaiacol, veratric acid, vanillic acid, cinnamic acid, p-coumaric acid, ferulic acid, and sinapic acid. In addition, the effects of different concentrations of ferulic acid on growth of Cupriavidus sp. B-8 were studied. The growth of Cupriavidus sp. B-8 is better under the condition of lower concentration. High-performance liquid chromatography (HPLC) analysis reveals that above 95% of ferulic acid is degraded within 12 h by Cupriavidus sp. B-8. Based on identification of biodegradation intermediates and further metabolites, the biodegradation pathway of ferulic acid by Cupriavidus sp. B-8 was proposed. Ferulic acid is initially converted to 4-vinylguaiacol, and further oxidized to vanillic acid and protocatechuic acid.

Biodegradation of ferulic acid by a newly isolated strain of Cupriavidus sp. B-8

The invention discloses a bacterial strain Cupriavidus sp B-8 for processing high-density papermaking black liquor, which has the collection number of CGMCC (China General Microbiological Culture Collection) No4240 The inventor collects Wu kingdom bamboo slip soak solution with plaque in the three kingdoms period, which is collected in the Changsha Bamboo Slips Museum, and uses the Wu kingdom bamboo slip soak solution as raw material, and one bacterial strain capable of growing on a culture medium which takes the alkali lignin as the only carbon source is obtained by accumulation culture, isolation, purification and screening The bacteria strain can be directly used for processing high-density alkaline straw pulp papermaking black liquor which is not subjected to any materialization preprocessing, and the COD (Chemical Oxygen Demand) of 30,000mg/L of the high-density alkaline straw pulp papermaking black liquor with the initial pH value of 11 and chroma of 8,500 can be lowered by 418% within five days

Huan Zhang

Papers

Characterization and genomic analysis of kraft lignin biodegradation by the beta-proteobacterium Cupriavidus basilensis B-8

Kraft lignin biodegradation by Novosphingobium sp. B-7 and analysis of the degradation process.

Characterization of a newly isolated Bacterium Pandoraea sp. B-6 capable of degrading kraft lignin

Biodegradation of ferulic acid by a newly isolated strain of Cupriavidus sp. B-8

Bacterial strain Cupriavidus sp. B-8 for processing high-density papermaking black liquor and application thereof