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Selected levansucrases (LSs) were investigated for their ability to catalyze the transfructosylation of lactose/sucrose into lactosucrose and fructooligosaccharides (FOSs). Additionally, dairy by-products, including whey permeate (WP) and milk permeate (MP), were assessed for their effectiveness as lactose sources. LSs from Gluconobacter oxydans (LS1), Vibrio natriegens (LS2), Novosphingobium aromaticivorans (LS3), and Burkholderia graminis (LS4) were utilized in three transfructosylation reactions that combined sucrose with either lactose, WP, or MP. All LSs demonstrated a higher transfructosylation activity than hydrolytic one, except for V. natriegens LS2 in the presence of sucrose and MP/sucrose. Furthermore, the bioconversion efficiency of lactose/sucrose into lactosucrose and FOSs exhibited varying time courses and end-product profiles. Both the acceptor specificity of LS and the thermodynamic equilibrium of its reaction modulated the end-product profile. V. natriegens LS2 resulted in the highest lactosucrose production of 328 and 251 g/L with lactose/sucrose and WP/sucrose, respectively. Our results revealed the potential of LS-catalyzed transfructosylation for the biocatalytic production of both lactosucrose and FOSs from abundant biomasses., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Laccase can catalyze the oxidative cross-linking of peptides, which is useful in the production of proteinaceous materials with enhanced functional properties. However, the kinetics and the pathway of this reaction remain unclear. In the present study, laccase-catalyzed oxidative cross-linking reaction was investigated through a combination of computational analysis, kinetic studies and end-product profiling using selected substrate models, including peptide AG-10 (AKKIVSDGNG) (without tyrosine) derived from lysozyme and tyrosine-containing peptide ST-10 (SYMTDYYLST) from potato protein (patatin), and tyrosine. Both laccases from Trametes versicolor (LacTv) and Coriolus hirsutus (LacCh) were used as biocatalysts. Laccase exhibited higher binding affinity and catalytic efficiency (k cat /K m ) towards ST-10 and AG-10 than tyrosine. Among the laccases, LacCh showed higher k cat towards the substrate models than LacTv. Through the molecular docking, this result was attributed to the presence of the ASN206 at the cavity of LacCh. The end product profiles reveal the formation of homo-oligomers (> 5 units) of ST-10 in the reaction catalyzed by LacTv, while polymerization was favored by LacCh. These cross-linked products were identified to have a mix of oligo-tyrosine linkages. In contrast, the cross-linking of AG-10 required the presence of ferulic acid as mediator, which resulted in the formation of hetero-oligomers and polymers of AG-10. The knowledge obtained in the present study provide insight into an effective reaction for peptide cross-linking., (Copyright © 2020 Elsevier Inc. All rights reserved.)