No abstract

This experiment was carried out to study the carcass characteristics, chemical composition and fatty acid profile of the Longissimus muscle (LM) of bulls (10) and steers (17) finished in a pasture system. Animals (1/2 Zebu vs. 1/2 Aberdeen Angus) were fed in a pasture system (Hermatria altissima) and with a supplement of soybean meal, cracked corn, urea, limestone and mineral salts, twice a day. Both animal groups were slaughtered at 27 months of age, with an average 508.88 kg of live weight. Final weight, hot carcass weight and texture were similar (p>0.05) between bulls and steers. Carcass dressing, fat thickness, color and marbling were higher (p<0.02) in steers. Conversely, the Longissimus area was greater (p<0.05) in bulls. Moisture levels were higher (p<0.01) in bulls. Ash, crude protein, total lipids and total cholesterol levels were higher (p<0.10) in steers. C14:0, C16:0, C16:1 n-7 and C18:1 n-9 fatty acids percentages were higher (p<0.06) in steers.

BackgroundLignin is a heterogeneous polymer representing a renewable source of aromatic and phenolic bio-derived products for the chemical industry. However, the inherent structural complexity and recalcitrance of lignin makes its conversion into valuable chemicals a challenge. Natural microbial communities produce biocatalysts derived from a large number of microorganisms, including those considered unculturable, which operate synergistically to perform a variety of bioconversion processes. Thus, metagenomic approaches are a powerful tool to reveal novel optimized metabolic pathways for lignin conversion and valorization.ResultsThe lignin-degrading consortium (LigMet) was obtained from a sugarcane plantation soil sample. The LigMet taxonomical analyses (based on 16S rRNA) indicated prevalence of Proteobacteria, Actinobacteria and Firmicutes members, including the Alcaligenaceae and Micrococcaceae families, which were enriched in the LigMet compared to sugarcane soil. Analysis of global DNA sequencing revealed around 240,000 gene models, and 65 draft bacterial genomes were predicted. Along with depicting several peroxidases, dye-decolorizing peroxidases, laccases, carbohydrate esterases, and lignocellulosic auxiliary (redox) activities, the major pathways related to aromatic degradation were identified, including benzoate (or methylbenzoate) degradation to catechol (or methylcatechol), catechol ortho-cleavage, catechol meta-cleavage, and phthalate degradation. A novel Paenarthrobacter strain harboring eight gene clusters related to aromatic degradation was isolated from LigMet and was able to grow on lignin as major carbon source. Furthermore, a recombinant pathway for vanillin production was designed based on novel gene sequences coding for a feruloyl-CoA synthetase and an enoyl-CoA hydratase/aldolase retrieved from the metagenomic data set.ConclusionThe enrichment protocol described in the present study was successful for a microbial consortium establishment towards the lignin and aromatic metabolism, providing pathways and enzyme sets for synthetic biology engineering approaches. This work represents a pioneering study on lignin conversion and valorization strategies based on metagenomics, revealing several novel lignin conversion enzymes, aromatic-degrading bacterial genomes, and a novel bacterial strain of potential biotechnological interest. The validation of a biosynthetic route for vanillin synthesis confirmed the applicability of the targeted metagenome discovery approach for lignin valorization strategies.Electronic supplementary materialThe online version of this article (10.1186/s13068-018-1073-4) contains supplementary material, which is available to authorized users.

This experiment was carried out to evaluate the carcass characteristics, chemical composition and fatty acid profile of the Longissimus muscle (LM) of three cattle genetic groups (Purunã, PUR, 11; 1/2 Purunã vs. 1/2 British, PUB, 6 and 1/2 Charolais vs. 1/2 Caracu, CHC, 10) finished in pasture systems. The field work took place at the Lapa Research Farm of the Agronomic Institute of Paraná, in the city of Lapa, south Brazil. The animals were fed during the winter with corn silage, cottonseed meal, cracked corn, urea, limestone and mineral salts as sources of protein, as well as an energy supplement, in pasture systems of Brachiaria decumbens Stapf. The animal groups were slaughtered at 20 months of age, at 501±22.6 kg live weight. CHC bulls had higher (p<0.05) final weight than PUR and PUB bulls. Hot carcass weight was similar (p>0.10) between PUR and PUB. Hot carcass dressing percentage was higher (p<0.05) for PUB bulls than for PUR and CHC bulls. On the other hand, hot carcass dressing percentage was similar (p>0.05) between PUR and CHC bulls. Fat thickness was similar (p>0.10) among all genetic groups. However, the Longissimus area of CHC bulls was greater (p<0.05) than in PUR and PUB genetic groups. The genetic groups did not affect (p>0.10) the marbling of Longissimus. There was no observed difference (p>0.10) in moisture, ash, crude protein and total cholesterol contents among the three genetic groups. On the other hand, the total lipid percentage was higher (p<0.05) for the PUB genetic group in comparison with PUR and CHC. CLA percentage was highest for PUR animals. However, total CLA amounts were not altered by the different genetic groups.

No abstract