Enhanced enzymatic saccharification of pretreated biomass using glycerol thermal processing (GTP)

Glycerol organosolv pretreatment can unlock lignocellulosic biomass for production of fermentable sugars: Present situation and challenges

The complex structure of lignocellulosic biomass forms the recalcitrance to prevent the embedded holo-cellulosic sugars from undergoing the biodegradation. Therefore, a pretreatment is often required for an efficient enzymatic lignocellulosic hydrolysis. Recently, glycerol organosolv (GO) pretreatment is revealed potent in selective deconstruction of various lignocellulosic biomass and effective improvement of enzymatic hydrolysis. Evidently, the GO pretreatment is capable to modify the structure of dissolved components by glycerolysis, i.e., by trans-glycosylation onto glyceryl glycosides and by hydroxylation grafting onto glyceryl lignin. Such modifications tend to protect these main components against excessive degradation, which can be mainly responsible for the obviously less fermentation inhibitors arising in the GO pretreatment. This pretreatment can provide opportunities for valorization of emerging lignocellulosic biorefinery with production of value-added biochemicals. Recent advances in GO pretreatment of lignocellulosic biomass followed by enzymatic hydrolysis are reviewed, and perspectives are made for addressing remaining challenges.

Organosolv Pretreatment of Sorghum Stalks Using Glycerol

Glycerol is a promising low-cost solvent for biomass pretreatment since a large amount of glycerol is generated as a by-product in the biodiesel industry. Pretreatment is a method of disintegration of the recalcitrant structure of biomass to enhance the accessibility of cellulose and hemicelluloses to enzymes for complete saccharification. During pretreatment, glycerol breaks the lignin carbohydrate complex and selectively solubilizes lignin. Thus, the glycerol pretreatment improves the accessibility of cellulose to cellulases leading to higher sugar yields. The glycerol pretreatment is carried out at high temperature (>190 °C) to disintegrate the structure of biomass. The glycerol pretreatment in the presence of acid or base catalyst such as H₂SO₄ or NaOH results in lower pretreatment temperature and higher glucan hydrolysis. This chapter describes the methodology to carry out glycerol pretreatment of sorghum biomass with or without acid/alkali as catalyst and the basic calculations to determine the efficiency of the pretreatment.

The solid-state physicochemical properties and biogas production of the anaerobic digestion of corn straw pretreated by microwave irradiation

The effect of different temperatures used in microwave pretreatment on enhancing methane production of corn straw was comparatively studied in this paper through the analysis of the physicochemical properties of the pretreated materials and the methane yield during anaerobic digestion. Analytic methods such as scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction were performed to detect the surface chemistry of the pretreated corn straw. The results indicated that microwave pretreatment could effectively disrupt the lignocellulosic structure to release cellulose, hemicellulose, and related derivatives and make them available for the process of anaerobic digestion. The outcome of the methanogenic assay demonstrated that methane production could be significantly improved by 73.08% concerning the variation of the temperatures in microwave pretreatment. This study provides technical support for pretreatment methods of lignocellulose materials and deems that microwave pretreatment boosts methane yield efficiently during the process of anaerobic digestion of lignocellulosic materials.

Yellow mombin and jackfruit seeds residues applied in the production of reducing sugars by a crude multi-enzymatic extract produced by Penicillium roqueforti ATCC 101110

BACKGROUND

As an alternative to the use of widely investigated agro-industrial residues, the present study aimed to promote the valorization of two selected residues, yellow mombin seed (YS) and jackfruit seed (JS), as a result of their enhanced performance.

RESULTS

YS was applied as a solid state substrate for Penicillium roqueforti ATCC 101110 cultivation (25 °C, A_w = 0.963, 10⁷ spores g^-1 and 142 h) to produce a crude multi-enzymatic extract (CE-YS) containing activities of CMCase = 31.95 U g^-1 , xylanase = 56.85 U g^-1 , exoglucanase = 5.55 U g^-1 and FPase = 24.60 U g^-1 . CE-YS was then applied to six different residues saccharification and the best performance was obtained with jackfruit seed residue (JS), which was selected for enzymatic saccharification. The highest productivity of reducing sugars expressed as glucose (6.26 mg g^-1 h^-1 ) was obtained under the conditions: 40.7 g L^-1 JS, 5 mmol L^-1 MgCl₂ , 65 °C, 120 rpm, pH 3.0 (citrate buffer 50 mmol L^-1 ) and 18 h.

CONCLUSION

The residues, YS and JS, can be used satisfactorily for the production of bioproducts of great industrial applicability, such as crude extracts (containing cellulolytic enzymes) and RS (which can be converted, for example, into bioethanol). © 2020 Society of Chemical Industry.

Enhancement of bioethanol production from Moso bamboo pretreated with biodiesel crude glycerol: Substrate digestibility, cellulase absorption and fermentability

Utilization of sustainable energy is limited by energy requirement for the manufacturing of renewable fuels. Moso bamboo was pretreated with industrially derived crude glycerol obtained from different sources at 150/160 °C for 3 h. This bamboo, pretreated with base biodiesel glycerol with pressure filtration removal method, showed a high glucose yield of 94.95% and an ethanol yield of 73.10% of the theoretical. Major glycerol content was removed by pressure filtration, leaving a small amount of fatty acid soap in the pretreated sample, which formed an emulsion that reduced lignin redisposition onto the biomass surface and effectively blocked lignin absorption of cellulase, allowing greater enzymatic hydrolysis and fermentation system function. The surface was more hydrophilic and a higher lignin removal was achieved: 39.24% with base biodiesel glycerol pretreatment compared to 26.08% with sodium hydroxide glycerol pretreatment. This study provides a useful and cost-effective process, BBGP, for high-yield ethanol production.

New insight into the effect of fungal mycelia present in the bio-pretreated paddy straw on their enzymatic saccharification and optimization of process parameters

Assessment of Pleurotus florida efficiency on paddy straw pretreatment and optimization of saccharification parameters were studied. P. florida growth was monitored by the estimation of fungal cell wall component (glucosamine). The control bio-pretreatment sample showed high glucosamine content by 397 mg/g in 28 days of incubation. But, the Inhibitor Mediated Biological (IMB) Pretreatment showed 29% lower result due to the inhibition of cellulase enzyme limits mycelial penetration rate inside the paddy straw. Fungal components present inside the pretreated straw renders nonspecific interactions with the hydrolytic enzymes during saccharification process and reducing the hydrolysis efficiency. IMB pretreated paddy straw showed maximum saccharification efficiency up to 75.3% with optimized condition (Biomass loading- 10% (w/v), Enzyme loading- 20 FPU/g and saccharification time - 72 h) than control pretreatment sample. Thus, the study brings out new insight into the effect of fungal residues inside the bio-pretreated paddy straw during enzymatic saccharification to improve the efficiency.

Utilization of Lignocellulosic Biomass via Novel Sustainable Process

In this review, we show novel methods for utilizing lignocellulosic biomass, polysaccharides, and lignin. Firstly, the simultaneous enzymatic saccharification and comminution (SESC) of plant materials is described as an extraction method for lignocellulosic biomass that does not require toxic reagents or organic solvents. Secondly, we demonstrate the material utilization of non-deteriorated lignocellulosic biomass extracted by SESC, such as for sugar and ethanol synthesis, and as a heatproof filler. Finally, we exhibit the use of a functional monomer (e.g., in disinfection chemicals, cesium chelation, and building blocks for polymers), 2-pyrone-4,6-dicarboxylic acid, derived from lignin via metabolic degradation.

A novel sono-assisted acid pretreatment of chili post harvest residue for bioethanol production

The objective of the present study was to develop a sono-assisted acid pretreatment strategy for the effective removal of lignin and hemicelluloses and to improve the sugar yield from chili post harvest residue. Operational parameters that affect the pretreatment efficiency were studied and optimized. Inhibitor analysis of the hydrolyzate revealed that major fermentation inhibitors like furfural, hydroxymethyl furfural and organic acids like citric acid, succinic acid and propionic acid were absent. Changes in structural properties of the biomass were studied in relation to the pretreatment process using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) analysis, and the changes in chemical composition was also monitored. The biomass pretreated with the optimized novel method yielded 0.465g/g of reducing sugars on enzymatic hydrolysis. Fermentation of the non-detoxified hydrolysate yielded 2.14% of bioethanol with a fermentation efficiency of 71.03%.

Revealing the thermal sensitivity of lignin during glycerol thermal processing through structural analysis

A woody biomass was treated in glycerol between 200 and 240 °C in an anhydrous environment to denature the biomass for biopolymer fractionation.