Improvement of antioxidant activity of Morchella esculenta protein hydrolysate by optimized glycosylation reaction

ABSTRACT

Morchella protein hydrolysate (MPH) is produced from an edible and medicinal fungus, Morchella esculenta (L.), and exhibits antioxidant activity. In order to further improve the antioxidant activity of MPH, glycosylation of MPH was conducted by applying response surface methodology via the Maillard reaction (MR). Optimum glycosylation conditions were confirmed as: xylose/MPH mass ratio of 3.7:1, pH 11.80, and reaction time 60 min. The glycosylation of MPH under these optimized conditions was characterized by Fourier transform infrared spectroscopy, fluorescence spectroscopy, and scanning electron microscopy. In vitro antioxidant activity tests showed that glycosylated MPH had significantly enhanced antioxidant activities compared to the native MPH, heat-treated MPH, or a MPH–xylose mixture. Collectively, these results indicate that glycosylation by the MR can improve the antioxidant activity of MPH, making it a novel source of natural antioxidants with excellent developmental prospects as a functional food.

RESUMEN

La proteína hidrolizada de Morchella (MPH) se produce a partir de un hongo comestible y medicinal, Morchella esculenta (L.), constatándose que la misma posee actividad antioxidante. Con el fin de mejorar su actividad antioxidante se realizó la glicosilación de la MPH utilizando la metodología de superficies de respuesta mediante la reacción de Maillard. En este sentido, se verificó que las condiciones óptimas para la glicosilación fueran: relación de masa xilosa/MPH de 3.7:1, pH de 11.80 y tiempo de reacción de 60 min. Alcanzadas estas condiciones optimizadas, se caracterizó la glicosilación de la MPH empleando espectroscopía infrarroja transformada de Fourier, espectroscopía de fluorescencia y microscopía electrónica de barrido. Las pruebas de actividad antioxidante in vitro indicaron que, en comparación con la MPH nativa, la MPH tratada térmicamente o una mezcla de MPH-xilosa, la MPH glicosilada mostró un aumento significativo de sus actividades antioxidantes. En conjunto, estos resultados constatan que la glicosilación mediante la reacción de Maillard puede mejorar la actividad antioxidante de la MPH, convirtiéndola en una novedosa fuente de antioxidantes naturales que, además, exhibe excelentes posibilidades de ser desarrollada como alimento funcional.

KEYWORDS:

• Morchella esculenta
• protein hydrolysate
• glycosylation
• response surface methodology
• antioxidant activity

PALABRAS CLAVE:

• Morchella esculenta
• proteína hidrolizada
• glicosilación
• metodología de superficies de respuesta
• actividad antioxidante

Acknowledgments

This work was supported by the Doctorate Fellowship Foundation of Nanjing Forestry University, the Natural Science Foundation of Anhui Provincial Department of Education (KJ2017A515); the Postgraduate Research & Practice Innovation Program of Jiangsu Province (KYLX15_0916); and the Program of Key Discipline in Anhui Science and Technology University (No. AKZDXK2015B02).

Disclosure statement

No potential conflict of interest was reported by the authors

Additional information

Funding

This work was supported by the Doctorate Fellowship Foundation of Nanjing Forestry University, the Natural Science Foundation of Anhui Provincial Department of Education [Grant Number KJ2017A515], the Postgraduate Research and Practice Innovation Program of Jiangsu Province [Grant Number KYLX15_0916], and the Program of Key Discipline in Anhui Science and Technology University [Grant Number AKZDXK2015B02].