Biodetoxification of Lignocellulose Hydrolysate for Direct Use in Succinic Acid Production.

The pretreatment of lignocellulosic biomass with acid generates phenolic and furanyl compounds that function as toxins by inhibiting microbial growth and metabolism. Therefore, it is necessary to detoxify acid-pretreated lignocellulosic biomass for better utilization. Among the various detoxification methods that are available, biodetoxification offers advantages that include mild reaction conditions and low energy consumption. In this study, a newly isolated Rhodococcus aetherivorans strain, N1, was found to effectively degrade various lignin-derived aromatic compounds, such as p-coumarate, ferulate, syringaldehyde, furfural, and 5-hydroxymethylfurfural. Furthermore, the metabolic pathway and genes responsible for this degradation were also identified. In addition, the overexpression of a demethylase (DesA) and 3,4-dioxygenase (DesZ) in strain N1 generated a recombinant strain, N1-S, which showed an enhanced ability to degrade syringaldehyde and 80.5% furfural, 50.7% 5-hydroxymethylfurfural, and 71.5% phenolic compounds in corn cob hydrolysate. The resulting detoxified hydrolysate was used directly as a feedstock for succinate production by Escherichia coli suc260. This afforded 35.3 g/l succinate, which was 6.5 times greater than the concentration afforded when nondetoxified hydrolysate was used. Overall, the results of this study demonstrate that strain N1-S is a valuable microbe for the biodetoxification of lignocellulosic biomass.

Microbial synthesis of pyrroloquinoline quinone.

Pyrroloquinoline quinone (PQQ) is a peptide-modified natural product. PQQ has important physiological functions such as anti-oxidation, anti-aging, and immunity enhancement. However, due to the lack of in-depth understanding of PQQ biosynthesis and regulation, inefficient PQQ production level limits its wide application. Accordingly, there is still an urgent need to develop high-yielding strains for synthesis of PQQ. This paper reviewed the research and development trends on the PQQ biosynthetic pathways, catalytic reaction mechanism of key enzymes, and the selection of high-yielding strains, which also prospects for the future construction of PQQ biosynthetic microbial cell factories.

High-Efficiency Reducing Strain for Producing Selenium Nanoparticles Isolated from Marine Sediment.

Selenium nanoparticles (SeNPs) are all important for research because they exhibit a higher degree of absorption and lower toxicity than that of their organic and inorganic forms. At present, there are few reports on marine strains that can reduce Se(IV) to generate Se(0). In this study, a strain that reduces sodium selenite to SeNPs with high efficiency was screened from 40 marine strains. The SeNPs-S produced by the whole cells and SeNPs-E produced by the extracellular extract were characterized by FTIR, UV, Raman, XRD and SEM. Based on the results, the two kinds of SeNPs exhibited obvious differences in morphology, and their surfaces were capped with different biomacromolecules. Due to the difference in shape and surface coating, opposite results were obtained for the antibacterial activity of SeNPs-S and SeNPs-E against Gram-positive and Gram-negative bacteria. Both SeNPs-S and SeNPs-E exhibited no obvious cytotoxicity at concentrations up to 100 µg/mL, but SeNPs-E retained lower cytotoxicity when its concentration increased to 200 µg/mL. This is the first report on the detailed difference between the SeNPs produced by whole cells and cell extracts.