Biogas production from wheat straw: community structure of cellulose-degrading bacteria

Abstract

Background: Wheat straw is one of the most abundant crop residues produced in the world, making it highly interesting as a substrate for biogas production. However, due to the complex structure, its degradability and gas yield are low. The degradability can be improved by pre-treatment, making the material more accessible to microbial degradation. Methods: To investigate the microbial response to straw as a feed stock for biogas production, this study examined the community structure of cellulose-degrading bacteria in lab-scale biogas digesters operating with manure, alone or in co-digestion with straw, with and without pre-treatment (steam-explosion) at different temperatures. The community was studied by targeting the functional gene encoding glycoside hydrolases of families 5 and 48 using T-RFLP, clone libraries and qPCR. Results: In general, bacteria belonging to the phyla Firmicutes and Bacteroidetes dominated the cellulose-degrading bacteria community in all digesters. The degree of similarity to the characterised bacteria was often low, and some clones were more closely related to the uncultured bacteria. The addition of straw, pre-treatment of straw and increasing operating temperature all affected the cellulose-degrading community structure, with differing responses in the cel48 and cel5 communities. Both communities changed in response to temperature, while only the cel5 community was affected by the addition of straw and cel48 community by straw pre-treatment. Conclusions: The addition of straw, pre-treatment of straw and operating temperature all affected the cellulosedegrading community in biogas digesters, but there were no major differences in the digester performance and gas yield.

Distribution of bacteria between different milk fractions, investigated using culture‐dependent methods and molecular‐based and fluorescent microscopy approaches

“…A 1 : 10 dilution (v/v) of DNA template was included for each sample to identify potential inhibition of the PCR reaction. Melt curve analysis and qPCR data processing were conducted as described previously (Sun et al ). To determine differences in abundance of different bacteria between skimmed and whole milk samples, the Welch's t ‐test was conducted using r (Welch ; R Core Team ).…”

“…The primers used in this study are listed in Table 2. The standard curve for each primer set was constructed using genomic DNA prepared from the corresponding strain as described previously (Sun et al 2014 Melt curve analysis and qPCR data processing were conducted as described previously (Sun et al 2013). To determine differences in abundance of different bacteria between skimmed and whole milk samples, the Welch's t-test was conducted using R (Welch 1947; R Core Team 2019).…”

Presence and Role of Anaerobic Hydrolytic Microbes in Conversion of Lignocellulosic Biomass for Biogas Production

“…summarised those approaches that are used to discover novel enzymes. More recently, Quantitative Polymerase Chain Reaction (Q-PCR), and sequencing methods were applied to determine the abundance of genes that are coding for GH families (Pereyra et al, 2010;Sun et al, 2013). Although these approaches showed the diversity of GH 48 families, the interpretation of these results should be carefully considered since the amplicon size of the targeted genes are relatively small and the diversity of GH 48 enzyme family is very large for designing successful primers.…”

Assessing the bioenergy potential of grassland biomass from conservation areas in England

“…Fungi, such as Trichodermo spp., can also be used to break down lignin before the biomass is added to the digester increasing biogas yields by up to 400% (Muthangya et al 2009; Wagner et al 2013). The bacteria used as inoculum in anaerobic digesters can also be optimized to break down lignin (Sun et al 2013). For example, Clostridium thermocellum, Comamonas testosteroni , and Pseudonocardia autotrophica contain endoglucanases, exoglucanases, xylanases, and lignolitic enzymes highly effective in degrading plant cell walls (Himmel et al 2007; Liao et al 2016).…”