Bioprospecting microbes and enzymes for the production of pterocarpans and coumestans

Abstract

The isoflavonoid derivatives, pterocarpans and coumestans, are explored for multiple clinical applications as osteo-regenerative, neuroprotective and anti-cancer agents. The use of plant-based systems to produce isoflavonoid derivatives is limited due to cost, scalability, and sustainability constraints. Microbial cell factories overcome these limitations in which model organisms such as Saccharomyces cerevisiae offer an efficient platform to produce isoflavonoids. Bioprospecting microbes and enzymes can provide an array of tools to enhance the production of these molecules. Other microbes that naturally produce isoflavonoids present a novel alternative as production chassis and as a source of novel enzymes. Enzyme bioprospecting allows the complete identification of the pterocarpans and coumestans biosynthetic pathway, and the selection of the best enzymes based on activity and docking parameters. These enzymes consolidate an improved biosynthetic pathway for microbial-based production systems. In this review, we report the state-of-the-art for the production of key pterocarpans and coumestans, describing the enzymes already identified and the current gaps. We report available databases and tools for microbial bioprospecting to select the best production chassis. We propose the use of a holistic and multidisciplinary bioprospecting approach as the first step to identify the biosynthetic gaps, select the best microbial chassis, and increase productivity. We propose the use of microalgal species as microbial cell factories to produce pterocarpans and coumestans. The application of bioprospecting tools provides an exciting field to produce plant compounds such as isoflavonoid derivatives, efficiently and sustainably.

Keywords: enzyme bioprospecting; isoflavonoids; microbial bioprospecting; microbial-based production; pterocarpans and coumestans.

FIGURE 1

Biosynthetic pathway for the production of coumestans and pterocarpans from the precursor, daidzein. Numbers for identifying carbon positions are shown for daidzein (isoflavonoid core) and medicarpin (carbon numbering varies with the formation of the fourth ring). The formation of a fourth ring between carbons 6 and 11 is highlighted in red. Abbreviations: OMT = isoflavanone 4′-O-methyltransferase; I3′H = isoflavone 3′-hydroxylase; I2′H = isoflavone 2′-hydroxylase; IFR = isoflavone reductase; PBS = pseudobaptigenin synthase; VR = Vestitone reductase; PTS = pterocarpan synthase; SOR = sophorol reductase; I3S = isoflav-3-ene synthase; HMM = (+)-6a-hydroxymaackiain 3-O-methyltransferase; DHPH = 3,9-dihydroxypterocarpan 6a-hydroxylase; GLS = glyceollin synthase; HPP = trihydroxypterocarpan prenyltransferase; D6aH = 3,9-dihydroxypterocarpan 6a-hydroxylase. Question marks indicates unknown enzymatic reactions.

FIGURE 2

Bioprospecting strategies for microbial and enzyme bioprospecting. Microbial bioprospecting allows the identification of best chassis, whereas enzyme bioprospecting identifies the best enzymes for the production of isoflavonoid derivatives using microbial cell factories.