Mucor circinelloides: a model organism for oleaginous fungi and its potential applications in bioactive lipid production

Abstract

Microbial oils have gained massive attention because of their significant role in industrial applications. Currently plants and animals are the chief sources of medically and nutritionally important fatty acids. However, the ever-increasing global demand for polyunsaturated fatty acids (PUFAs) cannot be met by the existing sources. Therefore microbes, especially fungi, represent an important alternative source of microbial oils being investigated. Mucor circinelloides-an oleaginous filamentous fungus, came to the forefront because of its high efficiency in synthesizing and accumulating lipids, like γ-linolenic acid (GLA) in high quantity. Recently, mycelium of M. circinelloides has acquired substantial attraction towards it as it has been suggested as a convenient raw material source for the generation of biodiesel via lipid transformation. Although M. circinelloides accumulates lipids naturally, metabolic engineering is found to be important for substantial increase in their yields. Both modifications of existing pathways and re-formation of biosynthetic pathways in M. circinelloides have shown the potential to improve lipid levels. In this review, recent advances in various important metabolic aspects of M. circinelloides have been discussed. Furthermore, the potential applications of M. circinelloides in the fields of antioxidants, nutraceuticals, bioremediation, ethanol production, and carotenoids like beta carotene and astaxanthin having significant nutritional value are also deliberated.

Keywords: Bioremediation; Carotenoids; Lipids; Metabolic engineering; Mucor circinelloides; Polyunsaturated fatty acids.

Fig. 1

Images of M. circinelloides a M. circinelloides growth pattern on agar plate b Microscopic image of lactophenol cotton blue-stained mycelia of M. circinelloides

Fig. 2

This picture demonstrates different pathways of carbon and lipid metabolism such as glycolysis, pentose phosphate pathway, TAG biosynthesis, transhydrogenase cycle, TCA cycle, fatty acid biosynthesis, fatty acid beta oxidation, carotenoid and steroid biosynthesis. Substrates have been abbreviated and enzymes have been numbered. Abbreviations of substrates, transporters and pathways are provided in Additional file 1: Table S1. List of numbers denoting different enzymes is provide in Additional file 2: Table S2

Fig. 3

PUFA formation pathways in microorganisms, based on traditional fatty acid synthase pathway. Fatty acid residues are synthesized by the FAS-enzyme complex from malonyl-CoA and acetyl-CoA. PUFAs are categorized into two groups, named as n-3 and n-6 series, depending on the location of the double bond with respect to the terminal -CH₃ group. PUFA pathway in M. circinelloides has been highlighted