Characterization of a Novel Myrosinase with High Activity from Marine Bacterium Shewanella baltica Myr-37.

Myrosinase can hydrolyze glucosinolates to generate isothiocyanates, which have cancer prevention and anti-cancer properties. The main sources of myrosinase are cruciferous plants. To further improve the efficiency of isothiocyanates preparation, it is necessary to explore novel sources of myrosinases. In this study, we described a bacterium, Shewanella baltica Myr-37, isolated from marine mud, capable of producing a novel myrosinase (Smyr37) with a molecular weight of 100 kDa. The crude enzyme of Smyr37 showed the highest activity at 50 °C and pH 8.0. The sinigrin- and glucoraphanin-hydrolyzing activities of Smyr37 were 6.95 and 5.87 U/mg, respectively. Moreover, when the reaction temperature was 40 °C and pH was 7.0, the crude enzyme of Smyr37 could efficiently degrade glucoraphanin into sulforaphane within 25 min with a yield of 0.57 mg/mL. The corresponding conversion efficiency of sulforaphane from glucoraphanin was 89%. In summary, S. baltica Myr-37 myrosinase Smyr37, a novel myrosinase, can be used in the preparation of isothiocyanates.

Improving the catalytic and mechanical performance of alginate catalyst through functionalization by aminopolycarboxylic acids.

Biomass-based aerogel catalysts have attracted extensive attention due to their high surface aera, continuous porous and environmental friendliness. However, their catalytic activity and mechanical strength are not satisfied for industrial applications. In this work, to solve the above two issues, a new kind of graphene oxide enhancediminodiacetic acid-functionalized Cu-cross-linked alginate (GO-Cu-SA-IDA) aerogel composites were prepared. The physicochemical property of the prepared alginate aerogel composites was characterized systematically, and their catalytic activities were studied in the hydroxylation of phenol. Results illustrated that compared with Cu-SA aerogels (∼16 %), the amount of loaded copper ion which played as the active sites in GO-Cu-SA-IDA aerogel composite was increased by 2 times (32.2 %). In addition, the mechanical strength of GO-Cu-SA-IDA was increased by 10 times. After functionalization, both the catalytic activity and mechanical strength of prepared alginate aerogel composites were enhanced successfully. In addition, the catalyst had been recycled five times with only 5.8 % loss of its catalytic activity, which provided a desirable material for next generation of catalysts.

Lactococcus garvieae FUA009, a Novel Intestinal Bacterium Capable of Producing the Bioactive Metabolite Urolithin A from Ellagic Acid.

Dietary polyphenol ellagic acid has anti-cancer and anti-inflammatory activities, and these biological activities require the conversion of ellagic acid to urolithins by intestinal microbes. However, few gut microbes are capable of metabolizing ellagic acid to produce urolithins, limiting the beneficial effects of ellagic acid on health. Here, we describe an intestinal bacterium Lactococcus garvieae FUA009 isolated from the feces of a healthy volunteer. It was demonstrated via HPLC and UPLC-MS analysis that the end product of ellagic acid metabolism of FUA009 was urolithin A. In addition, we also examined the whole genome sequence of FUA009 and then assessed the safety and probiotic properties of FUA009 based on a complete genome and phenotype analysis. We indicated that FUA009 was safe, which was confirmed by FUA009 being sensitive to multiple antibiotics, having no hemolytic activity, and being free of aggressive putative virulence factors. Moreover, 19 stress-responsive protein genes and 8 adhesion-related genes were predicted in the FUA009 genome. Furthermore, we demonstrated that FUA009 was tolerant to acid and bile salt by determining the cell viability in a stress environment. In summary, Lactococcus garvieae FUA009, as a novel UA-producing bacterium, not only contributes to the study of the metabolic pathway of ellagic acid but is also expected to be a novel probiotic candidate.

Rationally engineered chitin deacetylase from Arthrobacter sp. AW19M34-1 with improved catalytic activity toward crystalline chitin.

Chitin and its derivatives have anticoagulant, antimicrobial, and antioxidant properties, but the poor solubility of chitin limits its application in different fields. In this study, site-directed mutagenesis was performed to enhance the deacetylation activity of chitin deacetylases CDA from Arthrobacter (ArCE4). The mutant Mut-2-8 with Y172E/E200S/Y201W showed a 2.84- fold and 1.39-fold increase in catalytic efficiency (kcat/Km) for the deacetylation of (GluNAc)5 and α-chitin, respectively. These results demonstrated that the mutations significantly improved the activation of ArCE4 on crystalline chitin. The molecular docking study confirmed that the enhancement of catalytic efficiency is due to the extra two hydrogen bonds and one acetyl group. In summary, the activity of Mut-2-8 to insoluble chitin was significantly improved by reactional design, which is beneficial to resolve the issues of the expensive cost of the enzymes and low efficiency. Mut-2-8 exhibits potential applications in the chitosan industry.

Preparation and catalytic performance of alginate-based Schiff Base.

As a biomass polymer, alginate-based material has drawn considerable attention and been applied in many fields. However, the research on alginate-based Schiff Base metal complex is scarce. Herein, a novel alginate-based Schiff Base Cu (II) complex was prepared via oxidation and imidization of alginate by periodate and organic amine, respectively. In additon, their catalytic performance in phenol hydroxylation reaction was investgated. Results illustrated that degree of oxidation had significant influence on metal loaded content. Compared with alginate, the alginate-based Schiff Base has more reactive groups, and can stablize more Cu cations which endowed their better catalytic activities.