Thermo-mechanical fractionation of yellow poplar sawdust with a low reaction severity using continuous twin screw-driven reactor for high hemicellulosic sugar recovery

Comprehensive reutilization of Glycyrrhiza uralensis residue by extrusion-biological pretreatment for coproduction of flavonoids, cellulase, and ethanol

A continuous chemical-free green approach was investigated for the comprehensive reutilization of all components in herbal extraction residues (HERs), taking Glycyrrhiza uralensis residue (GUR) as an example. The GUR structural changes induced by mechanical extrusion which improve the specific surface area and enzyme accessibility of GUR. With 3 % pretreated GUR loading of high-tolerance Penicillium oxalicum G2. The reducing sugar yield of 11.45 g/L was achieved, along with an 81.06 % in situ enzymatic hydrolysis. Finally, 8.23 g/L bioethanol (0.40 g/g total sugar) was produced from GUR hydrolysates after 24 h fermentation of Pichia stipitis G32. The amount of functional medicinal ingredients extracted from GUR after hydrolysis (39.63 mg/g) was 37.69 % greater than that of un-pretreated GUR. In total, 1.49 g flavonoids, 294.36 U cellulase, and 14.13 g ethanol could be produced from 100 g GUR using this process, illustrating that this green and efficient process has the potential for industrial production.

Recent advances on physical technologies for the pretreatment of food waste and lignocellulosic residues

The complete deployment of a bio-based economy is essential to meet the United Nations' Sustainable Development Goals from the 2030 Agenda. In this context, food waste and lignocellulosic residues are considered low-cost feedstocks for obtaining industrially attractive products through biological processes. The effective conversion of these raw materials is, however, still challenging, since they are recalcitrant to bioprocessing and must be first treated to alter their physicochemical properties and ease the accessibility to their structural components. Among the full pallet of pretreatments, physical methods are recognised to have a high potential to transform food waste and lignocellulosic residues. This review provides a critical discussion about the recent advances on milling, extrusion, ultrasound, and microwave pretreatments. Their mechanisms and modes of application are analysed and the main drawbacks and limitations for their use at an industrial scale are discussed.

Bioconversion of Renewable Plant Biomass. Second-Generation Biofuels: Raw Materials, Biomass Pretreatment, Enzymes, Processes, and Cost Analysis

The review discusses various aspects of renewable plant biomass conversion and production of the second-generation biofuels, including the types of plant biomass, its composition and reaction ability in the enzymatic hydrolysis, and various pretreatment methods for increasing the biomass reactivity. Conversion of plant biomass into sugars requires the use of a complex of enzymes, the composition of which should be adapted to the biomass type and the pretreatment method. The efficiency of enzymatic hydrolysis can be increased by optimizing the composition of the enzymatic complex and by increasing the catalytic activity and operational stability of its constituent enzymes. The availability of active enzyme producers also plays an important role. Examples of practical implementation and scaling of processes for the production of second-generation biofuels are presented together with the cost analysis of bioethanol production.

Delignification of Pinecone and Extraction of Formic Acid in the Hydrolysate Produced by Alkaline Fractionation

The objectives of our research are to investigate the concept of delignification from pinecone through alkaline fractionation and then extraction of formic acid from the hydrolysate through esterification using ethanol. The pinecone is considered a promising material because of its relatively higher lignin content (35.80%) than other lignocellulosic biomass. The recovery yield of acid insoluble lignin (AIL) reached its maximum value of 79.20% at 8% NaOH, and the concentration of formic acid in the hydrolysate had its highest value under the same conditions. Moreover, the glucan content in fractionated solid remained high. The hydrolysate was subjected to esterification with ethanol under various reaction conditions for formic acid extraction, with solvent mixing ratio range: 1:1-1:4 v/v, reaction temperature range: 30-45 °C, and reaction time range: 60-100 min. Subsequently, the ethanol mixture (ethanol and ethyl formate) was recovered through distillation. The formic acid was extracted with more than 85% at mixing ratio of 1:2 and 45 °C for all reaction times. Furthermore, salt compounds composed mainly of Na and S were recovered because of its properties not soluble in ethanol solution.