Enhanced antioxidant activity of Chenopodium formosanum Koidz. by lactic acid bacteria: Optimization of fermentation conditions.

Hsing-Chun Kuo,Chang-Wei Hsieh,Shu-Han Yu,Hui-Wen Lin,Ho Ki Kwong,Hung-Yueh Chen,Yung-Lin Chu,Kuan-Chen Cheng,Hsien-Yi Hsu,Branislav T Šiler

doi:10.1371/journal.pone.0249250

Abstract

In this study, different probiotics commonly used to produce fermented dairy products were inoculated independently for Chenopodium formosanum Koidz. fermentation. The strain with the highest level of antioxidant activity was selected and the fermentation process was further optimized via response surface methodology (RSM). Lactobacillus plantarum BCRC 11697 was chosen because, compared to other lactic acid bacteria, it exhibits increased free radical scavenging ability and can produce more phenolic compounds, DPPH (from 72.6% to 93.2%), and ABTS (from 64.2% to 76.9%). Using RSM, we further optimize the fermentation protocol of BCRC 11697 by adjusting the initial fermentation pH, agitation speed, and temperature to reach the highest level of antioxidant activity (73.5% of DPPH and 93.8% of ABTS). The optimal protocol (pH 5.55, 104 rpm, and 24.4°C) resulted in a significant increase in the amount of phenolic compounds as well as the DPPH and ABTS free radical scavenging ability of BCRC 11697 products. The IC50 of the DPPH and ABTS free radical scavenging ability were 0.33 and 2.35 mg/mL, respectively, and both protease and tannase activity increased after RSM. An increase in lower molecular weight (<24 kDa) protein hydrolysates was also observed. Results indicated that djulis fermented by L. plantarum can be a powerful source of natural antioxidants for preventing free radical-initiated diseases.

Highlights

Djulis (Chenopodium formosanum Koidz.) is a traditional crop from the same genus as quinoa (Chenopodiun quinoa), and it is cultivated and consumed as food or used as a wine starter in Taiwan [1]
The results showed that all 10 strains of Lactic acid bacteria (LAB) promoted the antioxidant activity of djulis
The ABTS radical scavenging activity assay demonstrated that L. plantarum BCRC 11697 showed significantly higher ABTS radical scavenging activity (76.9%) compared to the control (64.2%) (p < 0.05)

Summary

Introduction

Djulis (Chenopodium formosanum Koidz.) is a traditional crop from the same genus as quinoa (Chenopodiun quinoa), and it is cultivated and consumed as food or used as a wine starter in Taiwan [1]. Reports have shown that djulis exhibits beneficial effects on anti-inflammation, anti-diabetes, anti-oxidation, and immune regulation [1, 2]. Bioactive components and pigments such as peptides, betacyanin (red), betaxanthins (yellow), and polyphenols contribute to the aforementioned effects. Other ingredients, such as rutin and chlorogenic acid, can restore the injury from UVB on HaCaT cells by reducing the level of interleukin-6 and reactive oxygen species (ROS) [3]. Several studies have indicated that LAB exhibit multiple functions, such as modulating gut health, improving liver function, and decreasing cholesterol levels and blood pressure [4,5,6]. Bianchi et al [9] reported that synbiotic fermented beverages combining quinoa and soy had favorable nutritional, rheological, and sensory characteristics

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Conclusion