Date Published: April 16, 2018
Publisher: Springer Berlin Heidelberg
Author(s): Jing Zhu, Lu Yan, Xiaoguang Xu, Yan Zhang, Junling Shi, Chunmei Jiang, Dongyan Shao.
To improve the production yield of (+)-pinoresinol (Pin), (+)-pinoresinol monoglucoside (PMG), and (+)-pinoresinol diglucoside (PDG), different methods were conducted, including co-culture with resveratrol-producing Alternaria sp. MG1 spores and addition of Tu-chung in a medium at the start of cultivation, ultrasound treatment (40 kHZ, 10 min) on 5-day culture, and addition of ethanol and sodium butyrate on Day 3, followed by cultivation for an additional period of 2 days. At the end of the cultivation period (5 days), the liquid phase was collected for product analysis. Cells were collected for the determination of gene expression levels and then used in bioconversion using resting cells for another period of 2 days. The liquid phase was measured to determine the output of the target products and the expression levels of the key genes related to the biosynthesis of these compounds. Consequently, co-culture with Alternaria MG1 and addition of Tu-chung bark in the medium efficiently increased Pin, PMG, and PDG production yield in the biosynthesis systems using potato dextrose broth medium and resting cells of Phomopsis sp. XP-8. The key genes related to the biosynthesis of these compounds were significantly upregulated. However, in the majority of cases, the addition of ethanol and sodium butyrate, and ultrasound treatment decreased the production yield of Pin, PMG, and PDG. The change in production yield was not consistently accompanied by a change in gene expression.
Lignan is a type of polyphenol that is widely found in plants. Pinoresinol [(+)-Pin] is a simple lignan converted from 2 coniferyl alcohol molecules via the phenylpropanoid pathway followed by the lignan biosynthesis pathway. Many lignan compounds and their derivatives have been found to have novel biological functions, including antibacterial and anticancer activities. Pin exhibits a considerably stronger anti-inflammatory activity against human intestinal Caco-2 cells, compared with other tested plant lignans (During et al. 2012). (+)-Pin and its glycosylation derivatives, pinoresinol diglucoside ((+)-1-pinoresinol 4,4′-di-O-β-d-glucopyranoside, PDG), have been identified as enterolactone precursors with preventive effects against breast cancer (Horn-Ross et al. 2001) and endometrial cancer (Gumma and Ramesh 2003). (+)-Pin has also exerted putative hypoglycemic effects via the inhibition of α-glucosidase (Wikul et al. 2012). PDG has been found to exhibit various pharmacological functions against hypertension (Luo et al. 2010) and osteoporosis (Saleem et al. 2005). After dietary consumption, PDG can be converted to enterolignans by intestinal microflora (Xie et al. 2003). As such, it can potentially reduce the risk of breast cancer (Xie et al. 2013) and other hormone-dependent cancers (Adlercreutz 2002).
Five methods were employed in the study to evaluate their effects on the yield of target products directly after cultivation in a PDB medium and in the bioconversion systems with only glucose and resting cells. The expression levels of the key genes related to the biosynthesis of Pin, PMG, and PDG were also measured to indicate the possible mechanisms underlying these effects. The outline of each approach is indicated in Fig. 1 and detailed below.Fig. 1Methods used in the study