Effect of initial moisture content and chip size on the bioconversion efficiency of softwood lignocellulosics

Abstract

Previous optimization strategies for the bioconversion of lignocellulosics by steam explosion technologies have focused on the effects of temperature, pH, and treatment time, but have not accounted for changes in severity brought about by properties inherent in the starting feedstock. Consequently, this study evaluated the effects of chip properties, feedstock size (40-mesh, 1.5 x 1.5 cm, 5 x 5 cm), and moisture content (12% and 30%) on the overall bioconversion process, and more specifically on the efficacy of removal of recalcitrant lignin from the lignocellulosic substrates following steam explosion. Increasing chip size resulted in an improvement in the solids recovery, with concurrent increases in the water soluble, hemicellulose-derived sugar recovery (7.5%). This increased recovery is a result of a decrease in the "relative severity" of the pretreatment as chip size increases. Additionally, the decreased relative severity minimized the condensation of the recalcitrant residual lignin and therefore increased the efficacy of peroxide fractionation, where a 60% improvement in lignin removal was possible with chips of larger initial size. Similarly, increased initial moisture content reduced the relative severity of the pretreatment, generating improved solids and hemicellulose-derived carbohydrate recovery. Both increased chip size and higher initial moisture content results in a substrate that performs better during peroxide delignification, and consequently enzymatic hydrolysis. Furthermore, a post steam-explosion refining step increased hemicellulose-derived sugar recovery and was most effectively delignified (to as low as 6.5%). The refined substrate could be enzymatically hydrolyzed to very high levels (98%) and relatively fast rates (1.23 g/L/h).

Silencing CHALCONE SYNTHASE in Maize Impedes the Incorporation of Tricin into Lignin and Increases Lignin Content

“…Klason lignin was determined using a modified Klason lignin analysis method as described previously (Cullis et al, 2004). Briefly, ground samples were solvent extracted (water [3 3 40 mL], 80% ethanol [3 3 40 mL], and acetone [1 3 40 mL]) and freeze dried for 2 d. Once dried, 0.2 g of dried and extractive-free samples was weighed into test tubes and treated with 3 mL of 72% sulfuric acid for 2 h, with stirring every 10 min.…”

Efeito do teor de umidade sobre o pré-tratamento a vapor e a hidrólise enzimática do bagaço de cana-de-açúcar

“…Conforme relatado por outros autores, [16][17][18][19][20] altos teores de umidade influenciaram de forma positiva a recuperação dos principais componentes da biomassa, mas sua influência foi negativa em relação ao percentual de hidrólise. No entanto, apesar disto, todos os substratos obtidos sob elevadas temperaturas e tempos de reação apresentaram conversão praticamente total em 72 h de hidrólise.…”

“…Além disso, os substratos obtidos a partir do material com alto teor de umidade apresentaram melhor desempenho frente à hidrólise enzimática. 19 Por outro lado, o aumento da umidade, de 12 para 80%, não apresentou mudanças significativas na composição química do bagaço de cana pré-tratado a vapor a 205 °C por 10 min, bem como nos rendimentos de hidrólise enzimática e de fermentação alcoólica. 20 O presente trabalho teve como objetivo contribuir para a elucidação do efeito do teor de umidade do bagaço de cana sobre o seu pré-tratamento a vapor e susceptibilidade à hidrólise enzimática, considerando que, sob condições industriais, o bagaço apresenta umidade de 100% (m/m, base seca) após a moagem para retirada do caldo.…”

High‐throughput microplate technique for enzymatic hydrolysis of lignocellulosic biomass

“…However, size reduction using a centrifugal mill for a short period of time (10-15 min) should largely allow preservation of molecular integrity on the ultra-structural level. Size reduction also influences pre-treatment severity, depending on type of pre-treatment Cullis et al, 2004;Zeng et al, 2005). Tenfold particle size reduction of untreated corn stover (1,000-100 mm) did improve digestibility by 10-15%.…”

“…However, for other pre-treatments that result in pre-treated biomass slurries (i.e., dilute-acid based treatments) it might be necessary to dry the pre-treated sample prior to milling or mill the sample prior to pretreatment. The effect of particle size has been reported to be significant for most pre-treatments Cullis et al, 2004;Elshafei et al, 1991;Zeng et al, 2005) due to easier accessibility of plant biomass by pre-treatment chemicals (i.e., acid or alkali). It might be thus necessary to re-optimize pre-treatment conditions for the finely ground biomass to prevent excessive degradation reactions.…”