Rapid Biodegradable Ionic Aggregates of Polyesters Constructed with Fertilizer Ingredients.

Synthetic biodegradable polyesters tend to undergo slow biodegradation under ambient natural conditions and, hence, have been rejected or even banned recently in ecofriendly applications. Here, we demonstrate the preparation of polyesters exhibiting enhanced biodegradability, which were generated through a combination of old controversial macromolecules and aggregate theories. H3PO4-catalyzed diacid/diol polycondensation afforded polyester chains bearing chain-end -CH2OP(O)(OH)2 and inner-chain (-CH2O)2P(O)(OH) groups, which were subsequently treated with M(2-ethylhexanoate)2 (M = Zn, Mg, Mn, and Ca) to form ionic aggregates of polyesters. The prepared ionic aggregates of polyesters, which were constructed with fertilizer ingredients (such as M2+ and phosphate), exhibit much faster biodegradability than that of the conventional polyesters under controlled soil conditions at 25 °C, while displaying comparable or superior rheological and mechanical properties.

Melanin biopolymer synthesis using a new melanogenic strain of Flavobacterium kingsejongi and a recombinant strain of Escherichia coli expressing 4-hydroxyphenylpyruvate dioxygenase from F. kingsejongi.

BACKGROUND: Melanins are a heterologous group of biopolymeric pigments synthesized by diverse prokaryotes and eukaryotes and are widely utilized as bioactive materials and functional polymers in the biotechnology industry. Here, we report the high-level melanin production using a new melanogenic Flavobacterium kingsejongi strain and a recombinant Escherichia coli overexpressing F. kingsejongi 4-hydroxyphenylpyruvate dioxygenase (HPPD). RESULTS: Melanin synthesis of F. kingsejongi strain was confirmed via melanin synthesis inhibition test, melanin solubility test, genome analysis, and structural analysis of purified melanin from both wild-type F. kingsejongi and recombinant E. coli expressing F. kingsejongi HPPD. The activity of F. kingsejongi HPPD was demonstrated via in vitro assays with 6 × His-tagged and native forms of HPPD. The specific activity of F. kingsejongi HPPD was 1.2 ± 0.03 µmol homogentisate/min/mg-protein. Bioreactor fermentation of F. kingsejongi produced a large amount of melanin with a titer of 6.07 ± 0.32 g/L, a conversion yield of 60% (0.6 ± 0.03 g melanin per gram tyrosine), and a productivity of 0.03 g/L·h, indicating its potential for industrial melanin production. Additionally, bioreactor fermentation of recombinant E. coli expressing F. kingsejongi HPPD produced melanin at a titer of 3.76 ± 0.30 g/L, a conversion yield of 38% (0.38 ± 0.03 g melanin per gram tyrosine), and a productivity of 0.04 g/L·h. CONCLUSIONS: Both strains showed sufficiently high fermentation capability to indicate their potential as platform strains for large-scale bacterial melanin production. Furthermore, F. kingsejongi strain could serve as a model to elucidate the regulation of melanin biosynthesis pathway and its networks with other cellular pathways, and to understand the cellular responses of melanin-producing bacteria to environmental changes, including nutrient starvation and other stresses.

Comparative Genomic Analysis of Agarolytic Flavobacterium faecale WV33T.

Flavobacteria are widely dispersed in a variety of environments and produce various polysaccharide-degrading enzymes. Here, we report the complete genome of Flavobacterium faecale WV33T, an agar-degrading bacterium isolated from the stools of Antarctic penguins. The sequenced genome of F. faecale WV33T represents a single circular chromosome (4,621,116 bp, 35.2% G + C content), containing 3984 coding DNA sequences and 85 RNA-coding genes. The genome of F. faecale WV33T contains 154 genes that encode carbohydrate-active enzymes (CAZymes). Among the CAZymes, seven putative genes encoding agarases have been identified in the genome. Transcriptional analysis revealed that the expression of these putative agarases was significantly enhanced by the presence of agar in the culture medium, suggesting that these proteins are involved in agar hydrolysis. Pangenome analysis revealed that the genomes of the 27 Flavobacterium type strains, including F. faecale WV33T, tend to be very plastic, and Flavobacterium strains are unique species with a tiny core genome and a large non-core region. The average nucleotide identity and phylogenomic analysis of the 27 Flavobacterium-type strains showed that F. faecale WV33T was positioned in a unique clade in the evolutionary tree.

Biosynthesis of ubiquinone compounds with conjugated prenyl side chains.

Enzymatic steps from two different biosynthetic pathways were combined in Escherichia coli, directing the synthesis of a new class of biomolecules--ubiquinones with prenyl side chains containing conjugated double bonds. This was achieved by the activity of a C(30) carotenoid desaturase, CrtN, from Staphylococcus aureus, which exhibited an inherent flexibility in substrate recognition compared to other carotenoid desaturases. By utilizing the known plasticity of E. coli's native ubiquinone biosynthesis pathway and the unusual activity of CrtN, modified ubiquinone structures with prenyl side chains containing conjugated double bonds were generated. The side chains of the new structures were confirmed to have different degrees of desaturation by mass spectrometry and nuclear magnetic resonance analysis. In vivo (14)C labeling and in vitro activity studies showed that CrtN desaturates octaprenyl diphosphates but not the ubiquinone compounds directly. Antioxidant properties of conjugated side chain ubiquinones were analyzed in an in vitro beta-carotene-linoleate model system and were found to be higher than the corresponding unmodified ubiquinones. These results demonstrate that by combining pathway steps from different branches of biosynthetic networks, classes of compounds not observed in nature can be synthesized and structural motifs that are functionally important can be combined or enhanced.