No abstract

No abstract

A yeast identified as Rhodotorula mucilaginosa strain IM-2 was able to degrade acetamiprid (AAP) and thiacloprid (THI) in sucrose mineral salt medium with half-lives of 3.7 and 14.8 days, respectively, while it did not degrade imidacloprid and imidaclothiz. Identification of metabolites indicated that R. mucilaginosa IM-2 selectively converted AAP and THI by hydrolysis of AAP to form an intermediate metabolite IM 1-3 and hydrolysis of THI to form an amide derivative, respectively. Metabolite IM 1-3 had no insecticidal activity, while the THI amide showed considerable insecticidal activity but was 15.6 and 38.6 times lower than the parent THI following oral ingestion and a contact test against the horsebean aphid Aphis craccivora , respectively. The inoculated R. mucilaginosa IM-2 displayed biodegradability of AAP and THI in clay soils.

Glutamic acid is an abundant amino acid that lends a characteristic umami taste to foods. In fermented foods, glutamic acid can be found as a free amino acid formed by proteolysis or as a non-proteolytic derivative formed by microorganisms. The aim of the present study was to identify different structures of glutamic acid derivatives in a typical fermented protein-based food product, soy sauce. An acidic fraction was prepared with anion-exchange solid-phase extraction (SPE) and analyzed by UPLC/MS/MS and UPLC/TOF-MS. α-Glutamyl, γ-glutamyl, and pyroglutamyl dipeptides, as well as lactoyl amino acids, were identified in the acidic fraction of soy sauce. They were chemically synthesized for confirmation of their occurrence and quantified in the selected reaction monitoring (SRM) mode. Pyroglutamyl dipeptides accounted for 770 mg/kg of soy sauce, followed by lactoyl amino acids (135 mg/kg) and γ-glutamyl dipeptides (70 mg/kg). In addition, N-succinoylglutamic acid was identified for the first time in food as a minor compound in soy sauce (5 mg/kg).