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• Japonica rice protein (JRBP)-catechin (CC) covalent complexes were prepared. • The functional properties of JRBP-CC can be improved by ultrasonic-treated JRBP. • The optimal ultrasonic treatment power is 200 W. • JRBP-CC showed enhanced emulsifying properties and antioxidant activity. Due to the existence of many disulfide bonds in japonica rice bran protein (JRBP) molecules, their solubility is poor, which seriously affects other functional properties. To improve the functional characteristics of JRBP molecules, they were processed by ultrasound technology, and JRBP-catechin (CC) covalent complex was prepared. The structural and functional properties of indica and japonica rice bran proteins and their complexes were compared; furthermore, the changes in the structural and functional properties of JRBP-CC under different ultrasound conditions were investigated. The results showed that compared with indica rice bran protein (IRBP), the secondary structure of JRBP-CC was very different, the water holding capacity (WHC) was higher, and the emulsification performance was better. Different ultrasound conditions had different effects on the functional properties of JRBP-CC. When the ultrasound power was 200 W, the λ max redshift of the JRBP-CC complex was the most significant, the particle size was the smallest, the absolute value of the zeta potential was the largest, and the hydrophobicity and microstructure of the JRBP-CC complex were the best. Concurrently, the maximum WHC and oil holding capacity (OHC) of JRBP-CC under these conditions were 7.54 g/g and 6.87 g/g, respectively. Moreover, the emulsifying activity index (EAI) and emulsifying stability index (ESI) were 210 m2/g and 47.8 min, respectively, and the scavenging activities of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and ABTS+ were 71.96 % and 80.07 %, respectively. [ABSTRACT FROM AUTHOR]

In recent years, photoelectrochemical (PEC) biosensors have shown great application prospects in biological analysis and food detection. In this work, we developed and tested a new PEC biosensor. Three-dimensional graphene oxide (3DGO) was generated and deposited on an indium tin oxides (ITO) electrode. The photoelectrically active poly[Nile blue] (PNb) was formed on this electrode by electropolymerization, and glycerol dehydrogenase (GDH) was immobilised to generate the GDH-PNb-3DGO-ITO biosensor. This newly developed PEC biosensor exhibited excellent photoelectric response to lipase activity under light conditions, with a detection range of 0.1–6 U/mL and a lower detection limit of 0.069 U/mL. When the GDH-PNb-3DGO-ITO sensor was used for PEC detection of lipase activity by the standard addition recovery method, the recovery rate of the standard addition was 98.68–105.41%, and the relative standard deviation (RSD) was 2.1–3.5%, with good storage stability and repeatability. Therefore, this work provides new ideas for the design and preparation of PEC biosensors and introduces a new detection method for monitoring lipase activity. [Display omitted] • Development of a PEC biosensor to detect lipase activity. • The fabricated biosensor has excellent optoelectronic properties. • The sensor has a low detection limit (0.069 U/mL), providing a platform for lipase activity detection. [ABSTRACT FROM AUTHOR]