Morphology and Structure of Hemp Fibre after Bioscouring

Hemp Stem Epidermis and Cuticle: From Waste to Starter in Bio-Based Material Development

Nowadays, hemp farmers are facing an urgent problem related to plant stem disposal after seed harvesting. In this work, the commonly discarded epidermis and cuticle of hemp stems were valorized, turning them towards a sustainable recycling and reuse, contributing to the circular economy concept. Cellulose deprived of amorphous regions was obtained by a green process consisting of an ethanolic ultrasound-assisted maceration followed by mild bleaching/hydrolysis. The obtained hemp cellulose was esterified with citric acid resulting in a 1.2-fold higher crystallinity index and 34 °C lower T_g value compared to the non-functionalized hemp cellulose. Green innovative biocomposite films were developed by embedding the modified cellulose into PLA by means of an extrusion process. The structural and morphological characterization of the obtained biocomposites highlighted the functionalization and further embedment of cellulose into the PLA matrix. Attenuated Total Reflectance–Fourier Transform Infrared spectroscopy (ATR-FTIR) results suggested physical and chemical interactions between PLA and the organic filler in the biofilms, observing a homogeneous composition by Field Emission-Scanning Electron Microscopy (FESEM). Moreover, some increase in thermal stability was found for biocomposites added with 5%wt of the hemp cellulose filler. The obtained results highlighted the feasible recovery of cellulose from hemp stem parts of disposal concern, adding value to this agro-waste, and its potential application for the development of novel biocomposite films to be used in different applications.

Sourcing Cannabis sativa L. by thermogravimetric analysis

Marijuana, dried and ground Cannabis, is the most consumed illicit drug in the world. Many undesirable and risky effects to human health are caused by its use. The medicinal use or legal recreational use of Cannabis has also been rising in many countries. These facts make traceability methodologies increasingly important whether for forensic use, such as drug trafficking eradication, or for quality control purposes of legal medicinal Cannabis. Consequently, the objective of this study was to analyze Cannabis by means of thermogravimetric analysis (TGA) in order to assess the capability of this technique to trace the geographical origin of Cannabis cultivated in Colorado, United States of America. TGA appears to be sensitive enough to detect the degradation/decarboxylation of cannabinoids and terpenes, at least to some extent; also, the degradation of cellulose, hemicellulose and lignin was indicated. Overall, the temperature ranges we analyzed using linear discriminant analysis showed high accuracies, with the 200 to 300 °C and 600 to 700 °C ranges achieving 100% accuracy.

Changes in hemp secondary fiber production related to technical fiber variability revealed by light microscopy and attenuated total reflectance Fourier transform infrared spectroscopy

Interest in hemp (Cannabis sativa L.) is increasing due to the development of a new range of industrial applications based on bast fibers. However the variability of bast fiber yield and quality represents an important barrier to further exploitation. Primary and secondary fiber content was examined in two commercial hemp varieties (Fedora 17, Santhica 27) grown under contrasted sowing density and irrigation conditions. Both growing conditions and hemp varieties impact stem tissue architecture with a large effect on the proportion of secondary fibers but not primary fibers. Attenuated total reflectance infrared spectroscopy allowed the discrimination of manually-isolated native primary fibers and secondary fibers but did not reveal any clustering according to growing conditions and variety. Infrared data were confirmed by wet chemistry analyses that revealed slight but significant differences between primary and secondary fiber cell wall composition. Infrared spectroscopy of technical fibers obtained after mechanical defibering revealed differences with native primary, but not secondary fibers and also discriminated samples obtained from plants grown under different conditions. Altogether the results suggested that the observed variability of hemp technical fibers could be partially explained by i) differences in secondary fiber production and ii) differential behavior during mechanical defibering resulting in unequal separation of primary and secondary fibers.

Improvement of the thermostability and activity of a pectate lyase by single amino acid substitutions, using a strategy based on melting-temperature-guided sequence alignment

In the vast number of random mutagenesis experiments that have targeted protein thermostability, single amino acid substitutions that increase the apparent melting temperature (Tm) of the enzyme more than 1 to 2 degrees C are rare and often require the creation of a large library of mutated genes. Here we present a case where a single beneficial mutation (R236F) of a hemp fiber-processing pectate lyase of Xanthomonas campestris origin (PL(Xc)) produced a 6 degrees C increase in Tm and a 23-fold increase in the half-life at 45 degrees C without compromising the enzyme's catalytic efficiency. This success was based on a variation of sequence alignment strategy where a mesophilic amino acid sequence is matched with the sequences of its thermophilic counterparts that have established Tm values. Altogether, two-thirds of the nine targeted single amino acid substitutions were found to have effects either on the thermostability or on the catalytic activity of the enzyme, evidence of a high success rate of mutation without the creation of a large gene library and subsequent screening of clones. Combination of R236F with another beneficial mutation (A31G) resulted in at least a twofold increase in specific activity while preserving the improved Tm value. To understand the structural basis for the increased thermal stability or activity, the variant R236F and A31G R236F proteins and wild-type PL(Xc) were purified and crystallized. By structure analysis and computational methods, hydrophobic desolvation was found to be the driving force for the increased stability with R236F.

Determination of carboxyl content in high-yield kraft pulps using photoacoustic rapid-scan Fourier transform infrared spectroscopy

Pinus radiata kraft pulps with varying carboxyl content were studied using Fourier transform infrared photoacoustic spectroscopy (FT-IR-PAS). The examined pulp samples, with Kappa number ranging from 20.8 to 128, originated from pulping experiments conducted in flow-through reactors utilizing varying effective alkali, temperature, and cooking time. A partial least-squares (PLS) analysis was used to formulate a model that correlates the spectral data with the carboxyl content of pulp. Using three principal components, the resultant PLS model could explain approximately 98.5% of the variance in the X-matrix (spectral features) and 96.8% of the variance in the Y-matrix (measured carboxyl content). The FT-IR-PAS technique in combination with PLS analysis predicts the carboxyl content of the pulps with a high degree of accuracy. This method is much faster than the conventional titration methods and also not destructive to the pulp sample.