Ultrasonic or Microwave Cascade Treatment of Medicinal Plant Waste

In this study, we present a strategy for valorizing lignocellulosic wastes (licorice root and willow bark) that result from industrial extraction of active principles using water as green solvent and aqueous NaOH solution. The wastes were submitted to severe ultrasound (US) and microwave (MW) treatments. The aim of these treatments was to extract the remaining active principles (using water as a solvent) or to prepare them for cellulose enzymatic hydrolysis to hexoses (performed in an NaOH aqueous solution). The content of glycyrrhizic acid and salicin derivatives in licorice root and willow bark wastes, respectively, were determined. The best results for licorice root were achieved by applying the US treatment for 5 min at 25 °C (26.6 mg glycyrrhizic acid/gDM); while, for willow bark, the best results were achieved by applying the MW treatment for 30 min at 120 °C (19.48 mg salicin/gDM). A degradation study of the targeted compounds was also performed and showed good stability of glycyrrhizic acid and salicin derivatives under US and MW treatments. The soluble lignin concentration prior to enzymatic hydrolysis, as well as the saccharide concentration of the hydrolyzed solution, were determined. As compared with the MW treatment, the US treatment resulted in saccharides concentrations that were 5% and 160% higher for licorice root and willow bark, respectively.

ISOLATION OF CELLULOLYTIC BACTERIA FROM SOIL AND VALORIZATION OF DIFFERENT LIGNOCELLULOSIC WASTES FOR CELLULASE PRODUCTION BY SUBMERGED FERMENTATION

Cellulases are known to convert cellulose into monomeric or dimeric structures, hence playing an important role in bioethanol production, along with their applications in textile and paper industries. This study was directed towards the isolation and screening of cellulase producing bacteria from different soil samples on CMC (carboxymethyl cellulose) agar plates, followed by Gram’s iodine staining. Six strains showed clear zones of hydrolysis on CMC agar plates. Isolates were identified as Bacillus megaterium, Pseudomonas stutzeri, Bacillus aerius, Bacillus paralichniformis, Bacillus flexus, and Bacillus wiedmanni by 16S rRNA gene sequencing. These strains were cultivated by submerged fermentation for cellulase production using various lignocellulosic wastes, such as corn cob, rice husk, wheat straw, seed pods of Bombax ceiba and eucalyptus leaves. Results showed that Pseudomonas stutzeri is the best cellulase producer among these strains. It offered the highest cellulase activity of 170.9±4.1 (IU/mL/min) in media containing eucalyptus leaves after 24 h of incubation at 37 °C, followed by Bacillus paralichniformis, Bacillus wiedmanni, Bacillus flexus, Bacillus aerius and Bacillus megaterium. These bacterial strains and lignocellulosic wastes could be potentially used for industrial exploitation, particularly in biofuels and textiles.