Synthesis of 2'-fucosyllactose from apple pomace-derived xyloglucan oligosaccharides by an α-L-fucosidase from Pedobacter sp. CAU209.

2'-Fucosyllactose (2'-FL) is known for its ability to provide various health benefits to infants, such as gut maturation, pathogen resistance, improved immunity, and nervous system development. However, the production of 2'-FL using α-L-fucosidases is hindered by the lack of low-cost natural fucosyl donors and high-efficiency α-L-fucosidases. In this work, a recombinant xyloglucanase from Rhizomucor miehei (RmXEG12A) was applied to produce xyloglucan-oligosaccharide (XyG-oligos) from apple pomace. Then, an α-L-fucosidase gene (PbFucB) was screened from the genomic DNA of Pedobacter sp. CAU209 and expressed in Escherichia coli. The capability of purified PbFucB to catalyze XyG-oligos and lactose to synthesize 2'-FL was further evaluated. The deduced amino acid sequence of PbFucB shared the highest identity (38.4%) with that of other reported α-L-fucosidases. PbFucB showed the highest activity at pH 5.5 and 35 °C. It catalyzed the hydrolysis of 4-nitrophenyl-α-L-fucopyranoside (pNP-Fuc, 20.3 U mg-1), 2'-FL (8.06 U mg-1), and XyG-oligos (0.43 U mg-1). Furthermore, PbFucB demonstrated a high enzymatic conversion rate in 2'-FL synthesis with pNP-Fuc or apple pomace-derived XyG-oligos as donors and lactose as acceptor. Under the optimized conditions, PbFucB converted 50% of pNP-Fuc or 31% of the L-fucosyl residue in XyG-oligos into 2'-FL. This work elucidated an α-L-fucosidase that mediates the fucosylation of lactose and provided an efficient enzymatic strategy to synthesize 2'-FL either from artificial pNP-Fuc or natural apple pomace-derived XyG-oligos. KEY POINTS: • Xyloglucan-oligosaccharide (XyG-oligos) was produced from apple pomace by a xyloglucanase from Rhizomucor miehei. • An α-L-fucosidase (PbFucB) from Pedobacter sp. CAU209 shared the highest identity (38.4%) with reported α-L-fucosidases. •PbFucB synthesized 2'-FL using apple pomace-derived XyG-oligos and lactose with a conversion ratio of 31%.

Electrochemical Determination of Nitrite by Au Nanoparticle/Graphene-Chitosan Modified Electrode.

A highly sensitive nitrite (NO2−) electrochemical sensor is fabricated using glassy carbon electrode modified with Au nanoparticle and grapheme oxide. Briefly, this electrochemical sensor was prepared by drop-coating graphene oxide-chitosan mixed film on the surface of the electrode and then electrodepositing a layer of Au nanoparticle using cyclic voltammetry. The electrochemical behavior of NO2− on the sensor was investigated by cyclic voltammetry and amperometric i-t curve. The results showed that the sensor exhibited better electrocatalytic activity for NO2− in 0.1 mol/L phosphate buffer solution (PBS) (pH 5.0). The oxidation peak current was positively correlated with NO2− concentration in the ranges of 0.9 µM to 18.9 µM. The detection limit was estimated to be 0.3 µM. In addition, the interference of some common ions (e.g., NO3−, CO32−, SO42−, Cl−, Ca2+ and Mg2+) and oxidizable compound including sodium sulfite and ascorbic acid in the detection of nitrite was also studied. The results show that this sensor is more sensitive and selective to NO2−. Therefore, this electrochemical sensor provided an effective tool for the detection of NO2−.

Challenge for the detection of microplastics in the environment.

As an emerging contaminant in the environment, microplastics have attracted worldwide attention. Although research methods on microplastics in the environment have been reported extensively, the data on microplastics obtained cannot be comparable due to different methods. In this work, we critically reviewed the analytical methods of microplastics, including sample collection, separation, identification, and quantification. Manta trawl and tweezers or cassette corers are used to collect water samples and sediments, respectively. For biota sample, internal organs need to be dissected and separated to obtain microplastics. Density differences are often used to separate microplastics from the sample matrix. Visual classification is one of the most common methods for identifying microplastics, and it can be better detected by combining it with other instruments. However, they are not suitable for detection nanoplastics, which may lead to underestimation of risk. The abundance of microplastics varies with the detection method. Thus, the analytical methods for microplastics need to be standardized as soon as possible. Meanwhile, new methods for analyzing nanoplastics are urgently needed. PRACTITIONER POINTS: Sampling, separation, identification, and quantification are important procedures. The sampling and separation methods for microplastics need to be standardized. The organic matter can be removed by digestion to facilitate identification. Combine microscope with analytical instruments to better identify microplastics. There is still a challenge to quantification of smaller-sized plastic particles.

The Complex Toxicity of Tetracycline with Polystyrene Spheres on Gastric Cancer Cells.

Nowadays, microplastics (MPs) exist widely in the marine. The surface has strong adsorption capacity for antibiotics in natural environments, and the cytotoxicity of complex are poorly understood. In the study, 500 nm polystyrene (PS-MPs) and 60 nm nanoplastics (PS-NPs) were synthesized. The adsorption of PS to tetracycline (TC) was studied and their toxicity to gastric cancer cells (AGS) was researched. The adsorption experimental results show that PS absorbing capacity increased with increasing TC concentrations. The defense mechanism results show that 60 nm PS-NPs, 500 nm PS-MPs and their complex induce different damage to AGS cells. Furthermore, 600 mg/L PS-NPs and PS-MPs decline cell viability, induce oxidation stress and cause apoptosis. There is more serious damage of 60 nm PS-NPs than 500 nm PS-MPs in cell viability and intracellular reactive oxygen species (ROS). DNA are also damaged by 60 nm PS-NPs and PS-TC NPs, 500 nm PS-MPs and PS-TC MPs, and 60 nm PS-NPs damage DNA more serious than 500 nm PS-MPs. Moreover, 60 nm PS-NPs and PS-TC NPs seem to promote bcl-2 associated X protein (Bax) overexpression. All treatments provided us with evidence on how PS-NPs, PS-MPs and their compounds damaged AGS cells.