Optimisation of the biological pretreatment of wheat straw with white-rot fungi for ethanol production

Abstract

The biological pretreatment of lignocellulosic biomass for the production of bioethanol is an environmentally friendly alternative to the most frequently used process, steam explosion (SE). However, this pretreatment can still not be industrially implemented due to long incubation times. The main objective of this work was to test the viability of and optimise the biological pretreatment of lignocellulosic biomass, which uses ligninolytic fungi (Pleurotus eryngii and Irpex lacteus) in a solid-state fermentation of sterilised wheat straw complemented with a mild alkali treatment. In this study, the most important parameters of the mechanical and thermal substrate conditioning processes and the most important parameters of the fungal fermentation process were optimised to improve sugar recovery. The largest digestibilities were achieved with fermentation with I. lacteus under optimised conditions, under which cellulose and hemicellulose digestibility increased after 21 days of pretreatment from 16 to 100 % and 12 to 87 %, respectively. The maximum glucose yield (84 %) of cellulose available in raw material was obtained after only 14 days of pretreatment with an overall ethanol yield of 74 % of the theoretical value, which is similar to that reached with SE.

Ligninolytic enzymes: a biotechnological alternative for bioethanol production

“…The effectiveness of microbial delignification has been improved by adding an alkali treatment previous the fungal pretreatment. The alkali pretreatment benefits were the reduction of the process duration and the increment in the glucose and ethanol yield [61,62].…”

Use of new endophytic fungi as pretreatment to enhance enzymatic saccharification of Eucalyptus globulus

“…Basidiomycetes such as Trametes velutina, Pycnoporus sp. SYBC-L3, Pleurotus eryngii, Irpex lacteus, Ceriporiopsis subvermispora, Trametes versicolor and Phanerochaete chrysosporium have been used to treat various lignocellulosic biomasses and have enhanced hydrolysis yields (Cianchetta et al, 2014;Gui et al, 2013;Liu et al, 2013;López-Abelairas et al, 2013;Salvachúa et al, 2011;Wang et al, 2013a;Zhong et al, 2011). However, endophytic fungi (mainly ascomycetes) have not previously been used for this purpose.…”

“…The combination of fungal and physical or chemical pretreatments can potentially overcome recalcitrance, improving the yields of end products. Pretreatments with mild acid (Gui et al, 2013), alkali (Salvachúa et al, 2011;Yang et al, 2013;Zhong et al, 2011), organosolv (Muñoz et al, 2007), hydrogen peroxide (Yu et al, 2009), FeCl 3 (Wang et al, 2013b) and thermal treatments (López-Abelairas et al, 2013) have been combined with fungal pretreatments to increase saccharification yields. These combinations would also diminish the severity of chemical and/or physical pretreatments, minimising some of the disadvantages, such as the formation of inhibitory compounds (López-Abelairas et al, 2013;Wang et al, 2013a), and/or reducing fungal treatment times (Yu et al, 2009;Zhong et al, 2011).…”

Optimization of laccase production and its application in delignification of biomass

“…Whole fermentation lacking accumulation of glucose was found inside 72 h of simultaneous saccharification and fermentation (Alvira et al 2013). Use of ligninolytic fungi like Pleurotus eryngii and Irpex lacteus for biological pretreatment of wheat straw biomass was demonstrated indicating maximization of sugar yield and ethanol production and no furfural, 5-hydroxymethylfurfural or acetic or formic acids, the main inhibitors were detected in filtered supernatants after biological treatment (Lopez-Abelairas et al 2013). Pretreatment of Lantana camara with laccase from Pleurotus sp followed by simultaneous saccharification and fermentation by Saccharomyces cerevisiae yielded 5.14% (v/v) ethanol (Kuila and Banerjee 2014).…”