Microwave pretreatment of lignocellulosic biomass to release maximum phenolic acids

[EN] The objectives fixed by world’s governments concerning energy transition have aroused interest on lignocellulosic biomass utilization for bioenergy and green chemistry applications. However, due to their resistant structure, deconstructive pretreatments are necessary to render possible biological conversions of these lignocellulosic residues. Microwave (MW) treatment has been reported as efficient in many biotechnology fields; biomass pretreatment for biorefinery purposes is another possible application. This work presents the effects of MW pretreatment on underexploited natural agri-food biomass of economic interest: wheat bran, miscanthus stalks and corn stalks. Various parameters were studied including solvent, power density, treatment duration, pressure. Effects were evaluated by a complete biomass characterization before and after treatment, with main focus on phenolic acids release. In the tested conditions and when compared to the high NaOH consumption reference extraction method for phenolic acids, the atmospheric pressure (open vessel) microwave treatment did not allow attaining high acid yields (Fig.1). The most important parameters for improving treatment efficiency were power density and solvent. In order to increase yields, microwave treatments under pressure were carried out to reach higher temperatures while taking care as to not exceed the acid denaturation temperature (150°C) and to avoid the formation of inhibitors. Phenolic acids yields and biomass composition are currently being processed and will be discussed.Authors would like to thank Nicolas Holfeltz, NH Verre France for his help in designing the microwave reactor. The authors also thank Yannick Sire from INRA Pech Rouge for phenolic acids analysis.Bichot, A.; Radoiu, M.; Bernet, N.; Mechin, V.; Delgenès, J.; García Bernet, D. (2019). Microwave pretreatment of lignocellulosic biomass to release maximum phenolic acids. En AMPERE 2019. 17th International Conference on Microwave and High Frequency Heating. Editorial Universitat Politècnica de València. 182-188. https://doi.org/10.4995/AMPERE2019.2019.9629OCS18218

Subtle Microwave-Induced Overheating Effects in an Industrial Demethylation Reaction and Their Direct Use in the Development of an Innovative Microwave Reactor

A systematic study of the conventional and microwave (MW) kinetics of an industrially relevant demethylation reaction is presented. In using industrially relevant reaction conditions the dominant influence of the solvent on the MW energy dissipation is avoided. Below the boiling point, the effect of MWs on the activation energy Ea and k0 is found nonexistent. Interestingly, under reflux conditions, the microwave-heated (MWH) reaction displays very pronounced zero-order kinetics, displaying a much higher reaction rate than observed for the conventionally thermal-heated (CTH) reaction. This is related to a different gas product (methyl bromide, MeBr) removal mechanism, changing from classic nucleation into gaseous bubbles to a facilitated removal through escaping gases/vapors. Additionally, the use of MWs compensates better for the strong heat losses in this reaction, associated with the boiling of HBr/water and the loss of MeBr, than under CTH. Through modeling, MWH was shown to occur inhomogeneously around gas/liquid interfaces, resulting in localized overheating in the very near vicinity of the bubbles, overall increasing the average heating rate in the bubble vicinity vis-à-vis the bulk of the liquid. Based on these observations and findings, a novel continuous reactor concept is proposed in which the escaping MeBr and the generated HBr/water vapors are the main driving forces for circulation. This reactor concept is generic in that it offers a viable and low cost option for the use of very strong acids and the managed removal/quenching of gaseous byproducts

SUDOSCAN: A Simple, Rapid, and Objective Method with Potential for Screening for Diabetic Peripheral Neuropathy.

Clinical methods of detecting diabetic peripheral neuropathy (DPN) are not objective and reproducible. We therefore evaluated if SUDOSCAN, a new method developed to provide a quick, non-invasive and quantitative assessment of sudomotor function can reliably screen for DPN. 70 subjects (45 with type 1 diabetes and 25 healthy volunteers [HV]) underwent detailed assessments including clinical, neurophysiological and 5 standard cardiovascular reflex tests (CARTs). Using the American Academy of Neurology criteria subjects were classified into DPN and No-DPN groups. Based on CARTs subjects were also divided into CAN, subclinical-CAN and no-CAN. Sudomotor function was assessed with measurement of hand and foot Electrochemical Skin Conductance (ESC) and calculation of the CAN risk score. Foot ESC (μS) was significantly lower in subjects with DPN [n = 24; 53.5(25.1)] compared to the No-DPN [77.0(7.9)] and HV [77.1(14.3)] groups (ANCOVA p<0.001). Sensitivity and specificity of foot ESC for classifying DPN were 87.5% and 76.2%, respectively. The area under the ROC curve (AUC) was 0.85. Subjects with CAN had significantly lower foot [55.0(28.2)] and hand [53.5(19.6)] ESC compared to No-CAN [foot ESC, 72.1(12.2); hand ESC 64.9(14.4)] and HV groups (ANCOVA p<0.001 and 0.001, respectively). ROC analysis of CAN risk score to correctly classify CAN revealed a sensitivity of 65.0% and specificity of 80.0%. AUC was 0.75. Both foot and hand ESC demonstrated strong correlation with individual parameters and composite scores of nerve conduction and CAN. SUDOSCAN, a non-invasive and quick test, could be used as an objective screening test for DPN in busy diabetic clinics, insuring adherence to current recommendation of annual assessments for all diabetic patients that remains unfulfilled