Prospect of metabolic engineering in enhanced microbial lipid production: review

Abstract

The use of fossil fuels has increasingly become associated with negative influences like detrimental environmental effects. This has made renewables, especially biofuels like biodiesel, a highly attractive substitute for energy generation. The industrial and economic potential of biodiesel-a lipid-based fuel-has increased interest and research into oleaginous microorganisms to synthesise and produce lipids. Effective identification and characterisation of a vast array of oleaginous microorganisms have led them to be employed for their efficient lipogenesis capability and ability to use a wide range of synthetic and non-expensive substrates. However, low lipid production has limited the use of microbially sourced lipids for biodiesel production at the industrial level. Nevertheless, the improvement and engineering of robust strains of these microbes through metabolic engineering have increased their lipid production capacity, leading to commercialising the lipids. This review provides a comprehensive outlook into the identification of different oleaginous microorganisms and their unique characteristics, which makes them highly valuable. An insight into the lipid biosynthesis pathways is provided and the role that several enzymes and regulators play in the metabolism of lipid accumulation. A detailed outlook is provided on the broad range of metabolic engineering approaches with regard to enhanced lipid production in several oleaginous microorganisms.

An Evolved Strain of the Oleaginous Yeast Rhodotorula toruloides, Multi-Tolerant to the Major Inhibitors Present in Lignocellulosic Hydrolysates, Exhibits an Altered Cell Envelope

“…The presence of toxic compounds in lignocellulosic hydrolysates (LCH) is among the main barriers affecting the efficiency of lignocellulose-based fermentation processes, in particular, to produce biofuels, hindering the production of intracellular lipids by oleaginous yeasts [1][2][3][4]. Microbial oils, produced by oleaginous yeasts, can reach up to 70% of dry cell weight [5][6][7] and are promising substitutes for vegetable oils for conversion into biodiesel [8][9][10]. The diverse growth and metabolism inhibitors present in lignocellulosic hydrolysates and the corresponding cultivation media belong to three major groups: weak acids, furan derivatives, and phenolic compounds arising from pretreatment, hydrolysis, and fermentation of lignocellulosic biomasses [1,11,12].…”

Bioengineering to Accelerate Biodiesel Production for a Sustainable Biorefinery

“…Recently, metabolic engineering has been employed to augment biofuel production. Studies have documented the engineering of metabolic pathways for biofuel generation [ 51 , 55 , 56 ].…”

“…The third-generation biofuel feedstock includes cyanobacteria, algae and seaweeds which are a significant source of the production of triglycerides, fatty acids, and lipids. These feedstocks have advantages such as large biomass production and a shorter harvesting cycle [ 55 ]. Microalgae, by utilizing sunlight and atmospheric carbon dioxide as energy and carbon sources, respectively, synthesize lipids.…”

“…The high cost of microalgal production and lipid extraction limits the use of microbially derived lipids for biodiesel production and industrial applications. Challenges in the domain of strain improvement to increase lipid production, growth and substrate requirements, utilization of non-expensive substrates and lipid extraction need to be addressed to augment biodiesel production [ 55 ]. The sustainability of algal biofuel production rests on the cultivation system, choice of algal species, source of nutrients, harvesting and downstream processing [ 57 , 58 ].…”

Exploring Yeast Diversity to Produce Lipid-Based Biofuels from Agro-Forestry and Industrial Organic Residues

“…To overcome these disadvantages, microbial lipids have gained attention in recent years. Besides not competing with food, their production is not susceptible to seasonal changes, the growth of microorganisms is much faster and microbial oils production can be optimised and controlled in bioreactors, with their composition being very similar to that of vegetable oils [ 9 , 10 , 11 ]. Among the best microbial candidates capable of producing lipids in high concentrations and with appropriate characteristics are oleaginous yeasts, described as those capable of accumulating more than 20% of cell dry weight in lipids [ 11 , 12 ].…”