Date Published: August 7, 2017
Publisher: Springer Berlin Heidelberg
Author(s): Ya-Qin Wei, Hong-Jian Yang, Rui-Jun Long, Zhi-Ye Wang, Bin-Bin Cao, Qin-Chang Ren, Tian-Tian Wu.
Anaerobic fungi reside in the gut of herbivore and synergize with associated methanogenic archaea to decompose ingested plant biomass. Despite their potential for use in bioconversion industry, only a few natural fungus–methanogen co-cultures have been isolated and characterized. In this study we identified three co-cultures of Piromyces with Methanobrevibacter ruminantium from the rumen of yaks grazing on the Qinghai Tibetan Plateau. The representative co-culture, namely (Piromyces + M. ruminantium) Yak-G18, showed remarkable polysaccharide hydrolase production, especially xylanase. Consequently, it was able to degrade various lignocellulose substrates with a biodegrading capability superior to most previously identified fungus or fungus–methanogen co-culture isolates. End-product profiling analysis validated the beneficial metabolic impact of associated methanogen on fungus as revealed by high-yield production of methane and acetate and sustained growth on lignocellulose. Together, our data demonstrated a great potential of (Piromyces + M. ruminantium) Yak-G18 co-culture for use in industrial bioconversion of lignocellulosic biomass.
With energy consumption continuing to rise and fossil fuels inevitably trending toward limitation, humanity is urged to find alternative energy resources. One most recent emerging focus of energy generation has been the use of biofuels which can be generated from sustainable biomass feedstocks (Tilman et al. 2009). On the top of the list of renewable biomass resources that are suitable for biofuel production is crop straw, which is ranked as the fourth largest energy resources after coal, oil and natural gas. The major structural component of crop straw is lignocellulose, a heterogeneous complex mainly consisting of two carbohydrate polymers (cellulose, hemicellulose), and an aromatic polymer (lignin) (Bayer et al. 2004). Currently, the bioconversion strategy is regarded as the most common approach for industrial utilization of lignocellulosic biomass, which explores natural microbial colonizers of lignocellulose or their lignocellulose-degrading enzymes to decompose the recalcitrant structural polymers to easily metabolizable monosaccharides which are subsequently converted to products (Balan 2014). Improving the bioconversion efficiency of lignocellulosic biomass has received increased attention from researchers in recent years.
Anaerobic fungi reside in the rumen of herbivore and synergize with associated methanogenic archaea to decompose ingested plant biomass. Given the relative short retention time of lignin tissues in the rumen, researchers have long speculated that rumen fungus–methanogen consortiums have acquired potent lignocellulose degradation capability attributable to natural selection. Thus, natural fungus–methanogen co-cultures may have the potential to be directly used in industrial bioconversion of renewable lignocellulosic biomass. Of equal importance, studies on these co-cultures may provide new insights into mechanistic aspects of fungal lignocellulolytic machinery, therefore facilitating the development of lignocellulolytic enzyme mixtures or complexes with improved biodegradation efficiency.