Characterization of a family 45 glycosyl hydrolase from Fibrobacter succinogenes S85

Expression and characterization of a family 45 glycosyl hydrolase from Fomitopsis pinicola and comparison to Phanerochaete chrysosporium Cel45A

To efficiently decompose biomass, fungi have developed various enzymatic and non-enzymatic strategies and are a source of versatile biocatalysts. The endoglucanases in glycosyl hydrolase CAZy family 45 (GH45) are known for their small size, a high thermostability and a broad substrate specificity that has been employed in textile and detergent industries. Here we report the heterologous expression and characterisation of an GH45 endoglucanase from the brown rot Fomitopsis pinicola and its direct comparison to an already characterised GH45 from the white rot Phanerochaete chrysosporium. Both enzymes were recombinantly expressed in Pichia pastoris and purified by two chromatographic steps. The biochemical characterisation highlighted the acidophilic character, with an optimal pH of 4, and a preference for amorphous substrates as carboxymethyl cellulose (CMC) and substrates containing β-1,4-glucans rather than the previously reported β-1,3/1,4-glucans lichenan and β-glucan. The dominating products from β-1,4-glucans were C3-C6 oligosaccharides, whereas from β-1,3/1,4-glucans glucose was the main reaction product. From the characterisation no differences between the brown rot and the white rot GH45 was evident.

Ninety-nine de novo assembled genomes from the moose (Alces alces) rumen microbiome provide new insights into microbial plant biomass degradation

The moose (Alces alces) is a ruminant that harvests energy from fiber-rich lignocellulose material through carbohydrate-active enzymes (CAZymes) produced by its rumen microbes. We applied shotgun metagenomics to rumen contents from six moose to obtain insights into this microbiome. Following binning, 99 metagenome-assembled genomes (MAGs) belonging to 11 prokaryotic phyla were reconstructed and characterized based on phylogeny and CAZyme profile. The taxonomy of these MAGs reflected the overall composition of the metagenome, with dominance of the phyla Bacteroidetes and Firmicutes. Unlike in other ruminants, Spirochaetes constituted a significant proportion of the community and our analyses indicate that the corresponding strains are primarily pectin digesters. Pectin-degrading genes were also common in MAGs of Ruminococcus, Fibrobacteres and Bacteroidetes and were overall overrepresented in the moose microbiome compared with other ruminants. Phylogenomic analyses revealed several clades within the Bacteriodetes without previously characterized genomes. Several of these MAGs encoded a large numbers of dockerins, a module usually associated with cellulosomes. The Bacteroidetes dockerins were often linked to CAZymes and sometimes encoded inside polysaccharide utilization loci, which has never been reported before. The almost 100 CAZyme-annotated genomes reconstructed in this study provide an in-depth view of an efficient lignocellulose-degrading microbiome and prospects for developing enzyme technology for biorefineries.

Effects of alfalfa flavonoids on the production performance, immune system, and ruminal fermentation of dairy cows

Objective

The objective of this study was to examine the effects of alfalfa flavonoids on the production performance, immunity, and ruminal fermentation of dairy cows.

Methods

The experiments employed four primiparous Holstein cows fitted with ruminal cannulas, and used a 4×4 Latin square design. Cattle were fed total mixed ration supplemented with 0 (control group, Con), 20, 60, or 100 mg of alfalfa flavonoids extract (AFE) per kg of dairy cow body weight (BW).

Results

The feed intake of the group receiving 60 mg/kg BW of AFE were significantly higher (p<0.05) than that of the group receiving 100 mg/kg BW. Milk yields and the fat, protein and lactose of milk were unaffected by AFE, while the total solids content of milk reduced (p = 0.05) linearly as AFE supplementation was increased. The somatic cell count of milk in group receiving 60 mg/kg BW of AFE was significantly lower (p<0.05) than that of the control group. Apparent total-tract digestibility of neutral detergent fiber and crude protein showed a tendency to increase (0.05<p≤0.10) with ingestion of AFE. Methane dicarboxylic aldehyde concentration decreased (p = 0.03) linearly, whereas superoxide dismutase activity showed a tendency to increase (p = 0.10) quadratically, with increasing levels of AFE supplementation. The lymphocyte count and the proportion of lymphocytes decreased (p = 0.03) linearly, whereas the proportion of neutrophil granulocytes increased (p = 0.01) linearly with increasing levels of dietary AFE supplementation. The valeric acid/total volatile fatty acid (TVFA) ratio was increased (p = 0.01) linearly with increasing of the level of AFE supplementation, the other ruminal fermentation parameters were not affected by AFE supplementation. Relative levels of the rumen microbe Ruminococcus flavefaciens tended to decrease (p = 0.09) quadratically, whereas those of Butyrivibrio fibrisolvens showed a tendency to increase (p = 0.07) quadratically in response to AFE supplementation.

Conclusion

The results of this study demonstrate that AFE supplementation can alter composition of milk, and may also have an increase tendency of nutrient digestion by regulating populations of microbes in the rumen, improve antioxidant properties by increasing antioxidant enzyme activities, and affect immunity by altering the proportions of lymphocyte and neutrophil granulocytes in dairy cows. The addition of 60 mg/kg BW of AFE to the diet of dairy cows was shown to be beneficial in this study.

Metatranscriptomics Reveals the Active Bacterial and Eukaryotic Fibrolytic Communities in the Rumen of Dairy Cow Fed a Mixed Diet

Ruminants have a unique ability to derive energy from the degradation of plant polysaccharides through the activity of the rumen microbiota. Although this process is well studied in vitro, knowledge gaps remain regarding the relative contribution of the microbiota members and enzymes in vivo. The present study used RNA-sequencing to reveal both the expression of genes encoding carbohydrate-active enzymes (CAZymes) by the rumen microbiota of a lactating dairy cow and the microorganisms forming the fiber-degrading community. Functional analysis identified 12,237 CAZymes, accounting for 1% of the transcripts. The CAZyme profile was dominated by families GH94 (cellobiose-phosphorylase), GH13 (amylase), GH43 and GH10 (hemicellulases), GH9 and GH48 (cellulases), PL11 (pectinase) as well as GH2 and GH3 (oligosaccharidases). Our data support the pivotal role of the most characterized fibrolytic bacteria (Prevotella, Ruminocccus and Fibrobacter), and highlight a substantial, although most probably underestimated, contribution of fungi and ciliate protozoa to polysaccharide degradation. Particularly these results may motivate further exploration of the role and the functions of protozoa in the rumen. Moreover, an important part of the fibrolytic bacterial community remains to be characterized since one third of the CAZyme transcripts originated from distantly related strains. These findings are used to highlight limitations of current metatranscriptomics approaches to understand the functional rumen microbial community and opportunities to circumvent them.

A thermostable GH45 endoglucanase from yeast: impact of its atypical multimodularity on activity

Background

The gene encoding an atypical multi-modular glycoside hydrolase family 45 endoglucanase bearing five different family 1 carbohydrate binding modules (CBM1), designated PpCel45A, was identified in the Pichia pastoris GS115 genome.

Results

PpCel45A (full-length open reading frame), and three derived constructs comprising (i) the catalytic module with its proximal CBM1, (ii) the catalytic module only, and (iii) the five CBM1 modules without catalytic module, were successfully expressed to high yields (up to 2 grams per litre of culture) in P. pastoris X33. Although the constructs containing the catalytic module displayed similar activities towards a range of glucans, comparison of their biochemical characteristics revealed striking differences. We observed a high thermostability of PpCel45A (Half life time of 6 h at 80°C), which decreased with the removal of CBMs and glycosylated linkers. However, both binding to crystalline cellulose and hydrolysis of crystalline cellulose and cellohexaose were substantially boosted by the presence of one CBM rather than five.

Conclusions

The present study has revealed the specific features of the first characterized endo β-1,4 glucanase from yeast, whose thermostability is promising for biotechnological applications related to the saccharification of lignocellulosic biomass such as consolidated bioprocessing.

Next-generation cellulosic ethanol technologies and their contribution to a sustainable Africa

The world is currently heavily dependent on oil, especially in the transport sector. However, rising oil prices, concern about environmental impact and supply instability are among the factors that have led to greater interest in renewable fuel and green chemistry alternatives. Lignocellulose is the only foreseeable renewable feedstock for sustainable production of transport fuels. The main technological impediment to more widespread utilization of lignocellulose for production of fuels and chemicals in the past has been the lack of low-cost technologies to overcome the recalcitrance of its structure. Both biological and thermochemical second-generation conversion technologies are currently coming online for the commercial production of cellulosic ethanol concomitantly with heat and electricity production. The latest advances in biological conversion of lignocellulosics to ethanol with a focus on consolidated bioprocessing are highlighted. Furthermore, integration of cellulosic ethanol production into existing bio-based industries also using thermochemical processes to optimize energy balances is discussed. Biofuels have played a pivotal yet suboptimal role in supplementing Africa's energy requirements in the past. Capitalizing on sub-Saharan Africa's total biomass potential and using second-generation technologies merit a fresh look at the potential role of bioethanol production towards developing a sustainable Africa while addressing food security, human needs and local wealth creation.

Characterization of the endoglucanase and glucomannanase activities of a glycoside hydrolase family 45 protein from Penicillium decumbens 114-2

The gene encoding a glycoside hydrolase (GH) family 45 endoglucanase (Cel45A) was cloned from P. decumbens 114-2 and expressed in Pichia pastoris. To our knowledge, this is the first report of characterization of a GH family 45 protein from Penicillium species. The purified recombinant enzyme showed a higher activity on konjac glucomannan (KGM) than on sodium carboxymethyl cellulose (CMC-Na) or phosphoric acid swollen cellulose (PASC). The highest hydrolytic activity was detected at pH5.0 on KGM and pH 3.5 on CMC-Na, indicating the mode of action on the two substrates may be different for Cel45A. The optimum temperatures on the two substrates were both 60 degrees C and about 90% relative activities were retained at 70 degrees C. Products released from PASC and CMC-Na were mainly cellobiose, cellotriose and cellotetraose. The protein with higher glucomannanase activity might help the efficient degradation of lignocellulose by P. decumbens in the natural state.

Quantitative analysis of cellulose degradation and growth of cellulolytic bacteria in the rumen

Ruminant animals digest cellulose via a symbiotic relationship with ruminal microorganisms. Because feedstuffs only remain in the rumen for a short time, the rate of cellulose digestion must be very rapid. This speed is facilitated by rumination, a process that returns food to the mouth to be rechewed. By decreasing particle size, the cellulose surface area can be increased by up to 10(6)-fold. The amount of cellulose digested is then a function of two competing rates, namely the digestion rate (K(d)) and the rate of passage of solids from the rumen (K(p)). Estimation of bacterial growth on cellulose is complicated by several factors: (1) energy must be expended for maintenance and growth of the cells, (2) only adherent cells are capable of degrading cellulose and (3) adherent cells can provide nonadherent cells with cellodextrins. Additionally, when ruminants are fed large amounts of cereal grain along with fiber, ruminal pH can decrease to a point where cellulolytic bacteria no longer grow. A dynamic model based on STELLA software is presented. This model evaluates all of the major aspects of ruminal cellulose degradation: (1) ingestion, digestion and passage of feed particles, (2) maintenance and growth of cellulolytic bacteria and (3) pH effects.