Cleaning carbohydrate impurities from lignin using Pseudomonas fluorescens

Abstract

A novel method of cleaning waste lignin biomass by means of selective biodegradation of cellulose and hemicellulose is investigated. This method uses Pseudomonas fluorescens (P. fluorescens), a non-pathogenic bacterium capable of producing cellulolytic enzymes, cleaving polymeric carbohydrates into free sugars and utilizing them as their carbon source. The growth of P. fluorescens on lignin biomass was confirmed by increasing cell count with time and visualized by scanning electron microscopy (SEM). Depletion of free sugars in the growth medium was measured by Technical Association of the Pulp and Paper Industry (TAPPI) methods and by time-of-flight secondary ion mass spectrometry (ToF SIMS), which showed a significant decrease in the carbohydrate content and an increase in the lignin fraction after P. fluorescens biodegradation. The molar mass distribution of lignin before and after the biodegradation of carbohydrate impurities showed no indication of lignin depolymerization. Our results strongly support the biodegradation of carbohydrate impurities from waste lignin by P. fluorescens as an effective, green and eco-friendly process.