Studies on delignification and inhibitory enzyme kinetics of alkaline peroxide pre-treated pine and deodar saw dust

Abstract

Delignification of lignocellulosic biomass by alkaline peroxide pre-treatment is a preliminary important step for an overall biomass fractionation process. In the present work, saw dusts are pre-treated by aqueous alkaline peroxide solution under different temperatures over a predetermined time. It is seen that Combined Pre-treatment (CP) removes a substantially higher quantity of lignin from biomass under a particular temperature. At elevated temperatures, the extent of delignification is observed much better. The % removal is: [PR:19.35%(30°C): 25.26%(50°C): 33.30%(100 °C)]; [CD: 14.64%(30°C): 23.64%(50°C):28.83%(100 °C)]. Batch kinetics is investigated with certain models and corresponding parameters are estimated. As pre-treatment severity is strongly correlated to the pre-treatment temperature, increased value of "potential degree of delignification" is observed at escalated temperatures. Kinetics of enzymatic hydrolysis of delignified biomass shows decreased product inhibition with increased substrate concentration under a particular enzyme loading.Starting with a combination of 50 g/L substrate concentration with an enzyme loading of 13.23 g/L, an optimum concentration of 17.2 g/L and 21.19 g/L of glucose are produced from Pinus roxburghii and Cedrus deodara respectively. Experimental data fit quite well with the competitive inhibition kinetics based theoretical models with r 2 ≥0.95. It is inferred that enzymes are competitively inhibited by glucose.

Kinetics of Lignin Removal from Rice Husk Using Hydrogen Peroxide and Combined Hydrogen Peroxide–Aqueous Ammonia Pretreatments

“…Therefore, a new measure, which is known as the degree of pretreatment (Dd) is being investigated. This parameter is used to predict a given biomass's maximal lignin solubilization ratio when a specific pretreatment method is used [25,27]. The kinetic model described in Equation ( 2) is expressed below:…”

“…In this model, there are three types of lignin, namely initial, bulk, and residual lignins that react in sequential order. It also proposes that distinct kinds of lignin degrade consecutively at the start and respond as pretreatment progress [25,27,35]. The use of HP and CHPA pretreatments of rice husk and the kinetics of two different techniques were examined and verified in this study.…”

“…Lignin removal is the most common chemical process that occurs during pretreatment. Several studies investigated the kinetics of lignin removal from biomass such as corn stover [22], wheat straw [23][24][25], rice husk [26], pine or deodar sawdust [27], oil palm empty fruit bunch [28][29][30], oak wood [31], cedarwood [32], and sugarcane bagasse [33][34][35][36] to improve pretreatment selectivity. However, the kinetics of lignin removal of hydrogen peroxide (HP) and the combination of hydrogen peroxide-aqueous ammonia (CHPA) pretreatments of rice husk have not been carried out.…”

“…The kinetic of pretreatment stage is essential to determine the economics of a process of reactor investment costs. In a pseudohomogeneous system with biomass, the H 2 O 2 solution produces a pseudohomogeneous system, and the pretreatment is a first-order reaction [27], which use two separate kinetic models. One of the models considers biomass as several kinds of polymers, with distinct phases of pretreatment assigned to various rate-controlling mechanisms of the whole process [35].…”

Response surface methodology (RSM) for optimization of thermochemical pretreatment method and enzymatic hydrolysis of deodar sawdust (DS) for bioethanol production using separate hydrolysis and co-fermentation (SHCF)

“…In a study by Bhavya et al, Cedrus deodara sawmill shavings were pyrolyzed in an atmosphere of hydrogen and nitrogen for bio-oil production [12]. Softwood tree biomass from Pinus roxburghii and Cedrus deodara were pretreated in another study using alkaline peroxide solution in order to study delignification kinetics at 30°C, 50°C, and 100°C temperatures, at a pH of 11.5, and an optimum concentration of 17.2 g/L and 21.19 g/L of glucose was produced from Pinus roxburghii and Cedrus deodara, respectively [18].…”