Sains Malaysiana 48(12)(2019): 2633–2640

http://dx.doi.org/10.17576/jsm-2019-4812-04

Preliminary Characterization of Exopolysaccharides Produced by Abortiporus biennis in Submerged Fermentation

(Pencirian Awal Eksopolisakarida yang Dihasilkan oleh Abortiporus biennis dalam Fermentasi Tenggelam)

ZHANGDE LONG¹, HONG LIU¹, JIGANG LI¹, JIANSHENG SUN¹, YUN XUE¹, ZHIZHONG HU¹, ZAN SU¹, CHUNPING XU² & JING-KUN YAN³*

¹Technical Center of China Tobacco Guangxi Industrial Co. Ltd, Nanning, Guangxi, 530001, China

²College of Food and Biology Engineering, Zhengzhou University of Light Industry, Zhengzhou, 450016, China

³School of Food & Biological Engineering, Jiangsu University, Zhenjiang, 212013, China

Received: 23 December 2018/Accepted: 8 October 2019

ABSTRACT

Abortiporus biennis is a rare edible and medicinal mushroom that is valuable in traditional Chinese medicine. Exopolysaccharides (EPSs) as valuable metabolites have been harvested from fermentation broths of A. biennis. However, studies on preliminary characterisations and bioactivities of A. biennis EPSs are lacking. In this study, therefore, the production, characteristics and bioactivity of EPSs produced by A. biennis in submerged fermentation were investigated. An EPS-1 was isolated and purified from the culture broth of A. biennis using a Sepharose CL-6B column chromatography. The molecular weight, monosaccharide composition, structural characteristics, chain conformation and thermal property of EPS-1 were determined by gel-filtration chromatography, gas chromatography-mass spectroscopy, Fourier-transform infrared spectroscopy, Congo red test and thermogravimetric analysis, respectively. The in vitro antioxidant and immunoregulation activities of the EPS-1 were evaluated by adopting DPPH and hydroxyl radical-scavenging assays, and analysing NO production in macrophage RAW 264.7 cells, respectively. Results showed that the culture medium containing 30 g/L lactose and 3.0 g/L tryptone had the most suitable carbon and nitrogen sources, respectively, for EPS production in A. biennis. The maximum EPS production (18.29 g/L) was obtained after 6 days of cultivation in a 5 L stirred-tank reactor under the most suitable culture medium. After purification, EPS-1 with 85.4% yield and 96.1% carbohydrate content was obtained from the culture broth of A. biennis. EPS-1 was characterised as a neutral heteropolysaccharide with a molecular weight of 22.07 kDa and is composed of glucose, mannose and galactose at a molar ratio of 3.3:2.0:1.0. EPS-1 with a relatively high thermal stability existed as a random coil conformation in the aqueous medium and possessed prominent radical-scavenging ability and macrophage stimulation activity in vitro. Therefore, EPS-1 could be explored as a functional ingredient with potential applications in food, medical and cosmetic industries.

Keywords: Abortiporus biennis; bioactivity; exopolysaccharides; preliminary characterisation; submerged fermentation

ABSTRAK

Abortiporus biennis adalah cendawan yang boleh dimakan dan boleh digunakan dalam ubatan yang sangat berharga dalam perubatan tradisi Cina. Eksopolisakarida (EPS) sebagai metabolit berharga telah dituai daripada kaldu fermentasi A. biennis. Walau bagaimanapun, kajian mengenai pencirian awal dan bioaktiviti A. biennis EPS adalah agak kurang. Oleh itu, dalam kajian ini, pengeluaran, ciri-ciri dan bioaktiviti EPS yang dihasilkan oleh A. biennis dalam fermentasi tenggelam telah dilakukan. EPS-1 telah dipencilkan dan ditulenkan daripada kultur kaldu A. biennis menggunakan kromatografi turus Sepharose CL-6B. Berat molekul, komposisi monosakarida, ciri struktur, penyesuaian rantai dan harta termal EPS-1 ditentukan menggunakan kromatografi penapisan gel, kromatografi gas-spektroskopi jisim, spektroskopi infra merah Fourier-tertransformasi, ujian Congo merah dan analisis termogravimetrik. Aktiviti antioksidan in vitro dan pengaturan imuno EPS-1 masing-masing ditentukan menggunakan asai DPPH dan hidroksil radikal skaveng serta menganalisis pengeluaran NO dalam sel makrofaj RAW 264.7. Hasil kajian menunjukkan bahawa kultur media yang mengandungi 30 g/L laktosa dan 3.0 g/L tripton mempunyai sumber karbon dan nitrogen yang paling sesuai untuk pengeluaran EPS dalam A. biennis. Pengeluaran EPS maksimum (18.29 g/L) diperoleh selepas penuaian selama 6 hari dalam reaktor tangki pengaduk 5L menggunakan kultur media yang paling sesuai. Selepas penulenan, EPS-1 dengan hasil sebanyak 85.4% dan kandungan karbohidrat sebanyak 96.1% telah diperoleh daripada kultur kaldu A. biennis. EPS-1 dicirikan sebagai heteropolisakarida neutral dengan berat molekul 22.07 kDa dan terdiri daripada glukosa, mannosa dan galaktosa pada nisbah molar 3.3:2.0:1.0. EPS-1 dengan kestabilan termal yang agak tinggi wujud dalam konformasi gegelung rawak dalam media akuas dan mempunyai keupayaan radikal skaveng yang menonjol serta aktiviti rangsangan makrofaj in vitro. Oleh itu, EPS-1 boleh diterokai sebagai bahan berfungsi dengan potensi aplikasi dalam industri makanan, perubatan dan kosmetik.

Kata kunci: Abortiporus biennis; bioaktiviti; eksopolisakarida; fermentasi tenggelam; pencirian awal

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*Corresponding author; email: jkyan_27@163.com