The role of pretreatment in improving the enzymatic hydrolysis of lignocellulosic materials.

Ainsworth and Bisby's Dictionary of the Fungi

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

Lignocellulosic materials are among the most promising alternative energy resources that can be utilized to produce cellulosic ethanol. However, the physical and chemical structure of lignocellulosic materials forms strong native recalcitrance and results in relatively low yield of ethanol from raw lignocellulosic materials. An appropriate pretreatment method is required to overcome this recalcitrance. For decades various pretreatment processes have been developed to improve the digestibility of lignocellulosic biomass. Each pretreatment process has a different specificity on altering the physical and chemical structure of lignocellulosic materials. In this paper, the chemical structure of lignocellulosic biomass and factors likely affect the digestibility of lignocellulosic materials are discussed, and then an overview about the most important pretreatment processes available are provided. In particular, the combined pretreatment strategies are reviewed for improving the enzymatic hydrolysis of lignocellulose and realizing the comprehensive utilization of lignocellulosic materials.

The role of pretreatment in improving the enzymatic hydrolysis

Carbon dioxide chemistry (in particular, capture and conversion) has attracted much attention from the scientific community due to global warming associated with positive carbon accumulation. The most widely used chemical absorption technique for carbon capture and storage/sequestration (CCS) would be essentially adopting amino-containing absorbents through formation of C–N bond in terms of mechanistic consideration. However, extensive energy input in desorption and compression process would be a crucial barrier to realize practical CCS. On the other hand, CO2 is very attractive as an environmentally friendly feedstock to replace the hazardous phosgene route for making commodity chemicals, fuels, and materials from a standpoint of green chemistry, whereas the reactions involving CO2 are commonly carried out at high pressure, which may not be economically suitable and also pose safety concerns. The challenge is to develop catalysts that are capable of activating CO2 under low pressure (preferably at 1 atm), and thus incorporating CO2 into organic molecules catalytically. We have proposed a carbon capture and utilization (CCU) strategy as an alternative approach to addressing the energy penalty problem in CCS. The essence of our strategy is to use captured CO2, also considered as the activated form of CO2, which could render this system suitable for accomplishing chemical transformation of CO2 under low pressure to avoid an additional desorption step. Indeed, CO2 could be activated through the formation of carbamate/alkyl carbonate with Lewis basic nitrogen species. In this review, we would like to discuss and update advances on CCU, particularly C–N bond formation with the production of oxazolidinones, quinazolines, carbamates, isocyanates and polyurethanes by using CO2 as C1 feedstock, and CO2 capture by amino-containing absorbents, including conventional aqueous solution of amine, chilled ammonia, amino-functionalized ionic liquids and solid absorbents such as amino-functionalized silica, carbon, polymers and resin, presumably leading to CO2's activation and thus subsequent conversion through C–N bond formation pathway.

Carbon dioxide utilization with C–N bond formation: carbon dioxide capture and subsequent conversion

Pretreatment of sugarcane bagasse with microwaves irradiation and its effects on the structure and on enzymatic hydrolysis

The role of copper(II) species in the oxidation of inorganic cyanide to cyanate and in the conversion of cyanate or urea into ethyl carbamate was investigated. The oxidation process has been shown to be independent from the dissolved oxygen. Elemental analysis and infrared spectroscopy have shown the formation of a mixed copper carbonate/hydroxide in the process of oxidation of cyanide to cyanate in water/ethanol. The complexation to CuII of cyanate formed upon cyanide oxidation makes the former more susceptible to nucleophilic attack from ethanol, with conversion into ethyl carbamate. Comparatively, urea has a minor role with respect to cyanide in the formation of ethyl carbamate. Therefore, the urea present in some samples of Brazilian sugar cane spirit (cachaca) has been shown to have almost no influence on the ethyl carbamate content of cachacas, which comes essentially from cyanide. FeII,III affords results similar to those found with CuII. Some suggestions are presented to avoid ethyl carbamate form...

Copper(II) catalysis in cyanide conversion into ethyl carbamate in spirits and relevant reactions.

AIMS To obtain new cellulases and xylanases from thermophilic fungi; evaluate their potential for sugarcane bagasse saccharification. METHODS AND RESULTS Thirty-two heat-tolerant fungi were isolated from the environment, identified (morphological/molecular tools) and the production of the enzymes was evaluated by solid state fermentation using lignocellulosic materials as substrates. Myceliophthora thermophila JCP 1-4 was the best producer of endoglucanase (357·51 U g(-1) ), β-glucosidase (45·42 U g(-1) ), xylanase (931·11 U g(-1) ) and avicelase (3·58 U g(-1) ). These enzymes were most active at 55-70°C and stable at 30-60°C. Using crude enzymatic extract from M. thermophila JCP 1-4 to saccharify sugarcane bagasse pretreated with microwaves and glycerol, glucose and xylose yields obtained were 15·6 and 35·13% (2·2 and 1·95 g l(-1) ), respectively. CONCLUSIONS All isolated fungi have potential to produce the enzymes; M. thermophila JCP 1-4 enzymatic extract have potential to be better explored in saccharification experiments. Pretreatment improved enzymatic saccharification, as sugar yields were much higher than those obtained from in natura bagasse. SIGNIFICANCE AND IMPACT OF THE STUDY Myceliophthora thermophila JCP 1-4 produces avicelase (not commonly found among fungi; important to hydrolyse crystalline cellulose) and a β-glucosidase resistant to glucose inhibition, interesting characteristics for saccharification experiments.

Thermophilic fungi as new sources for production of cellulases and xylanases with potential use in sugarcane bagasse saccharification.

Production and characterization of a milk-clotting protease in the crude enzymatic extract from the newly isolated Thermomucor indicae-seudaticae N31: (Milk-clotting protease from the newly isolated Thermomucor indicae-seudaticae N31)

http://www.scielo.br/pdf/bjm/v40n1/a05v40n1.pdf

Maurício Boscolo

Papers

Pretreatment of sugarcane bagasse with microwaves irradiation and its effects on the structure and on enzymatic hydrolysis

Copper(II) catalysis in cyanide conversion into ethyl carbamate in spirits and relevant reactions.

Thermophilic fungi as new sources for production of cellulases and xylanases with potential use in sugarcane bagasse saccharification.

Production and characterization of a milk-clotting protease in the crude enzymatic extract from the newly isolated Thermomucor indicae-seudaticae N31: (Milk-clotting protease from the newly isolated Thermomucor indicae-seudaticae N31)

Ligninases production by Basidiomycetes strains on lignocellulosic agricultural residues and their application in the decolorization of synthetic dyes