Arylsulfatase is useful in industrial agar processing by removing sulfate groups. A full-length arylsulfatase gene, designated ArySMA1, was obtained from marine bacteria Serratia sp. SM1. The ArySMA1 gene encoded a novel serine-type arylsulfatase and the enzymatic properties were characterized. The enzyme presented notable capacity of removing sulfate groups from natural algae substrates. Kinetic study suggested that the microscopic thermal inactivation rate of ArySMA1 in free form was smaller than that of the enzyme-substrate complex. The presence of substrate could unexpectedly accelerate ArySMA1 to deactivate at high temperature. Such phenomenon was opposite to many findings that substrate could stabilize enzymes against heat. Molecular dynamics simulation and ANS fluorescent assay indicated the substrate led the hydrophobic regions of the active site more flexible and the sulfate group of the substrate could retard the processivity of ArySMA1 catalysis. This study provides guidance for agar desulfation and down-stream processing industry.
In this study, phosphoric acid was used to replace hydrochloric acid which is widely reported in the production of whey protein isolate fibrils (WPF). The pH, temperature, and protein concentration for the phosphoric acid-induced fibrillation were optimized (4% w/v, pH 2.5, 90 °C). Under this condition, the mean particle size and molecular weight decreased significantly while the ζ-potential increased slightly, it suggested that the fibrillation was accompanied by hydrolysis . WPF was already formed via intermolecular interactions at 6 h, which exhibited a semiflexible and unbranched filament of about 10 nm in diameter. A few single-filament flexible fibrils (about 5 nm in diameter) formed at 24 h. Thioflavin T analysis supported by Intrinsic fluorescence showed that the use of phosphoric acid accelerated the fibrillation. The ANS fluorescence and Second-derivative UV–vis spectra indicated the increase in surface hydrophobicity, peaking after 12 h of heating. Compared with the hydrochloric acid induced, WPF induced by phosphoric acid exhibited a shorter lag phase and maintained a more stable dispersion state with a nanoscale particle size. The great interfacial properties and proper aspect ratio (length/diameter) provided the contribution that WPF effectively absorbed at the oil-water interface. Moreover, the emulsion stability of the WPF improved with increasing salt concentration. The phosphoric acid-induced WPF had the best emulsion stability at pH 5.5 which was further enhanced by proper heating.
危险品化学品经营许可证（带存储）