Fungal pretreatment of lignocellulose by Phanerochaete chrysosporium to produce ethanol from rice straw

Abstract

Phanerochaete chrysosporium is a wood-rot fungus that is capable of degrading lignin via its lignolytic system. In this study, an environmentally friendly fungal pretreatment process that produces less inhibitory substances than conventional methods was developed using P. chrysosporium and then evaluated by various analytical methods. To maximize the production of manganese peroxidase, which is the primary lignin-degrading enzyme, culture medium was optimized using response surface methodologies including the Plackett-Burman design and the Box-Behnken design. Fermentation of 100 g of rice straw feedstock containing 35.7 g of glucan (mainly in the form of cellulose) by cultivation with P. chrysosporium for 15 days in the media optimized by response surface methodology was resulted in a yield of 29.0 g of glucan that had an enzymatic digestibility of 64.9% of the theoretical maximum glucose yield. In addition, scanning electronic microscopy, confocal laser scanning microscopy, and X-ray diffractometry revealed significant microstructural changes, fungal growth, and a reduction of the crystallinity index in the pretreated rice straw, respectively. When the fungal-pretreated rice straw was used as a substrate for ethanol production in simultaneous saccharification and fermentation (SSF) for 24 h, the ethanol concentration, production yield and the productivity were 9.49 g/L, 58.2% of the theoretical maximum, and 0.40 g/L/h, respectively. Based on these experimental data, if 100 g of rice straw are subjected to fungal pretreatment and SSF, 9.9 g of ethanol can be produced after 96 h, which is 62.7% of the theoretical maximum ethanol yield.

The Confounding Effects of Particle Size and Substrate Bulk Density on Phanerochaete chrysosporium Pretreatment of Panicum virgatum

“…Control treatments were prepared identically (in triplicate) but were not inoculated with P. chrysosporium. All treatments and controls were placed in a 35 °C environment for 15 d (Bak et al 2009;Shi et al 2009). Xbale Tested treatments are represented by the table cells containing an X.…”

Fungus-Assisted Acetic Acid Pre-Treatment of Eucommia ulmoides Oliver Seed Shells for Enhancement of Enzymatic Hydrolysis

“…Improving the use of lignocellulosic material is an important solution for resource, energy, and environmental problems. Although hemicellulose and cellulose can be degraded into sugars, the direct enzymatic hydrolysis method is inefficient because lignocellulosic biomass is resistant to enzyme-mediated degradation (Bak et al 2009;Wang et al 2012;Gui et al 2013Gui et al , 2014.…”

“…There has been increasing interest in the biological pre-treatment of industrial wastes (Bak et al 2009;Gui et al 2014;Jin et al 2016), and microbial degradation of lignocellulosic material has become a hot research topic. Because they consume less energy and are less damaging to the environment, biological pre-treatments, including cellulosebinding domain treatment (Hall et al 2011) and fungal pre-treatment (Mosier et al 2002;Mosier et al 2005;Wyman et al 2005), are the most environmentally friendly processing approaches.…”

“…Additionally, most white-rot fungi degrade lignin and polysaccharides simultaneously, but some preferentially degrade lignin (Kuhad et al 1997;Guerra et al 2003). In this regard, Phanerochaete chrysosporium is the most widely used white-rot fungus for lignin degradation (Bak et al 2009;Zeng et al 2014;Saha et al 2016). As agricultural wastes and woody materials differ in their chemical and structural compositions, the best fungal strains and ligninolytic systems involved in the lignocellulose degradation process may differ between substrates (Li et al 2008;Saha et al 2016).…”

Direct Fungal Production of Ethanol from High-Solids Pulps by the Ethanol-fermenting White-rot Fungus Phlebia sp. MG-60

“…White rot fungi have a unique ability to decompose wood lignin via the secretion of extracellular lignin-degrading enzymes such as manganese peroxidase, lignin peroxidase, versatile peroxidase, and laccase (Lundell et al 2010). Thus, there are many reports focusing on the biological delignification pretreatment of lignocellulosic biomass for enzymatic saccharification and following fermentation (Bak et al 2009;Taniguchi et al 2005;Wan and Li 2011;Isroi et al 2011). Therefore, white-rot fungi, which have the ability to saccharify without addition of cellulase and to ferment cellulose simultaneously, may be potentially applicable for one-step fermentation of lignocellulosic biomass.…”