Valorization of Paper Industry Rejects by Combined Thermo-Chemical Pretreatment and Biological Conversion to L-Lysine

Abstract

Paper and pulp industry is one of the biggest industries that generate waste material and waste water. Conversion of the industrial waste to renewable products through green process is one of the recent trends for the production of renewable fuels and other industrially important bioproducts like bioethanol, biobutanol and bioplastics. In pulp and paper industry, the main process for the production of cellulose pulp is Kraft process and various wastes are generated during this process. These wastes mainly contain the plant biomass which consists carbohydrates like cellulose, hemicellulose and other components of the wood. The present work focuses on the potential of utilizing paper industry rejects for the production of amino acids. The paper rejects were pretreated using mild acids and hydrolyzed enzymatically using cellulases. The effect of the acid pretreatment and hydrolysis on cellulose fiber structure were studied. The pretreatment and hydrolysis yielded 37% sugar from the paper rejects and the glucose obtained was used for subsequent lysine fermentation. Maximum sugar yield was observed when the pretreatment was carried out in a laboratory autoclave at 121 ºC for 30 min at 15 lb pressure. When the pretreatment is carried out at higher temperature charring occurred which resulted in a reduction in glucose yield. The study was further outstretch by appraising the fermentability of using the paper reject hydrolyzateblended with CGXII synthetic medium in 1:1 ratio for L-lysine production using a strain of Corynebacterium glutamicum DM1729 which resulted in the production of 11.5 mg/ml lysine compared to 15.1 mg/ml obtained from pure synthetic medium.