Flax nanofibrils production via supercritical carbon dioxide pre‐treatment and enzymatic hydrolysis

Abstract

Flax fibres are an agro‐industrial waste available in large quantities in several countries around the world. This resource can be properly used. The goal of this work was to extract lignocellulosic nanosized flax fibres using an environmentally friendly process based on a combination of supercritical carbon dioxide (SC‐CO2) pre‐treatment and enzymatic hydrolysis. Raw flax fibres (RFF) were submitted to a SC‐CO2 pre‐treatment at various temperatures (ie, 70°C and 80°C) and pressures (ie, 20 and 37.7 MPa) for 60 minutes. The enzymatic hydrolysis was performed at 40°C for 24 hours in a pH 4.0 buffer. Cellulase, xylanase, pectinase, and viscozyme were used as hydrolytic enzymes. The as‐received raw flax fibres, SC‐CO2 pretreated flax fibres, and extracted lignocellulosic nanofibrils (LCNF) were characterized by Fourier transformed infrared spectroscopy (FTIR), x‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was shown that the effect of the SC‐CO2 pre‐treatment of flax fibres was two‐fold. It helped to disorganize biomass without changing its chemical composition and it increased access to enzymes to extract LCNF. The FTIR analysis showed no changes in the functional groups after SC‐CO2 pre‐treatment. The XRD characterization revealed that the crystallinity increased with the SC‐CO2 pre‐treatment and LCNF extraction. SEM images showed holes, cracks, and erosion on the surface of the SC‐CO2 pretreated flax fibres (SC‐CO2‐PFF). TEM evidenced the production of nano/micro‐sized fibril and fibril aggregates.

Physical and Enzymatic Hydrolysis Modifications of Potato Starch Granules

“…The supercritical CO 2 procedure was conducted in a one-liter stainless-steel high-pressure autoclave mounted with a diaphragm-type compressor (Superpressure, Newport Scientific, Inc., Jessup, MD, USA) operating at up to 6000 psi, and a thermostatic bath to achieve and maintain the CO 2 supercritical conditions (P > 1073 psi and T > 31 °C) as previously reported by Nlandu et al [ 33 ]. The pressure in the reactor was regulated by a Tescom valve placed between the compressor and the reactor.…”

Potato starch nanocrystal preparation via supercritical carbon dioxide pretreatment combined with enzymatic hydrolysis

“…The supercritical CO2 pretreatment was conducted in a 1 L stainless-steel highpressure autoclave mounted on a pressure pump capable of operating up to 6000 PSI, connected to a CO2 cylinder and a thermostatic bath, which made it possible to achieve and maintain the CO2 under supercritical conditions (a pressure greater than 1073 PSI and a temperature greater than 31 °C). In a typical run, according to the previous work of the authors, with slight modification (Nlandu et al 2019), the reactor was loaded with 20 g of native potato starch. Then liquid CO2 was aspirated from a cylinder equipped with a dip tube and pressurized by a motorized pump to 2000 PSI.…”

“…However, the SC-CO2-pretreatment induced a slight increase in the relative crystallinity of the potato starch. This could be related to the SC-CO2-pretreatment, which caused enough damage to the amorphous surface of potato starch, further exposing the crystalline regions and thus resulting in an increase in crystallinity (Nlandu et al 2019). Compared to the relative crystallinity of the native (A) and SC-CO2-pretreated starch (B) samples, the corresponding crystallinity of their nanocrystals (A1 and B1) was considerably increased.…”