Production Strategies and Applications of Microbial Single Cell Oils

Abstract

Polyunsaturated fatty acids (PUFAs) of the ω-3 and ω-6 class (e.g., α-linolenic acid, linoleic acid) are essential for maintaining biofunctions in mammalians like humans. Due to the fact that humans cannot synthesize these essential fatty acids, they must be taken up from different food sources. Classical sources for these fatty acids are porcine liver and fish oil. However, microbial lipids or single cell oils, produced by oleaginous microorganisms such as algae, fungi and bacteria, are a promising source as well. These single cell oils can be used for many valuable chemicals with applications not only for nutrition but also for fuels and are therefore an ideal basis for a bio-based economy. A crucial point for the establishment of microbial lipids utilization is the cost-effective production and purification of fuels or products of higher value. The fermentative production can be realized by submerged (SmF) or solid state fermentation (SSF). The yield and the composition of the obtained microbial lipids depend on the type of fermentation and the particular conditions (e.g., medium, pH-value, temperature, aeration, nitrogen source). From an economical point of view, waste or by-product streams can be used as cheap and renewable carbon and nitrogen sources. In general, downstream processing costs are one of the major obstacles to be solved for full economic efficiency of microbial lipids. For the extraction of lipids from microbial biomass cell disruption is most important, because efficiency of cell disruption directly influences subsequent downstream operations and overall extraction efficiencies. A multitude of cell disruption and lipid extraction methods are available, conventional as well as newly emerging methods, which will be described and discussed in terms of large scale applicability, their potential in a modern biorefinery and their influence on product quality. Furthermore, an overview is given about applications of microbial lipids or derived fatty acids with emphasis on food applications.

Acetate-detoxification of wood hydrolysates with alkali tolerant Bacillus sp. as a strategy to enhance the lipid production from Rhodosporidium toruloides

“…This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). lipids, since they grow fast and accumulate substantial amounts of lipids (Ochsenreither et al, 2016;Sitepu et al, 2014). Numerous microalgae are also recognised lipid producers since their productivity exceeds other photosynthetic organisms, without competing for arable land (Sibi et al, 2016).…”

“…Although oleaginous microorganisms are attractive sources of biodiesel feedstocks, the production of microbial lipids needs to be economically competitive with petroleum-based fuels (Sitepu et al, 2014). As certain cultivation conditions, mainly nutrient limitation in combination with carbon excess, trigger lipid accumulation in many oleaginous microorganisms (Ochsenreither et al, 2016), the carbon source in the growth medium is of central importance. The choice of carbon source plays a very important role in process economics and it was demonstrated that the use of glucose during lipid production from Rhodosporidium toruloides accounts for the 80% of the total raw material cost (Koutinas et al, 2014).…”

Oleaginous yeast Meyerozyma guilliermondii shows fermentative metabolism of sugars in the biosynthesis of ethanol and converts raw glycerol and cheese whey permeate into polyunsaturated fatty acids

“…Furthermore, it has been shown that fish sources of PUFA may contain heavy metals as contaminants . Alternatively, PUFA may be produced by microorganisms, both yeasts and bacteria, using bioprocess technology, which does not add environmental hazards and does not compete with food production . Agro‐industrial residues can be applied as substrates for bioprocess systems, further contributing to reduce production costs and environmental problems, as it is discussed below.…”

“…1 Alternatively, PUFA may be produced by microorganisms, both yeasts and bacteria, using bioprocess technology, which does not add environmental hazards and does not compete with food production. 6 Agro-industrial residues can be applied as substrates for bioprocess systems, further contributing to reduce production costs and environmental problems, as it is discussed below. The oil produced by oleaginous microorganisms, known as single cell oil (SCO), can be used in several industrial applications from food industries to biofuels, and their composition depend on the strain used and the cultivation conditions.…”

“…The oil produced by oleaginous microorganisms, known as single cell oil (SCO), can be used in several industrial applications from food industries to biofuels, and their composition depend on the strain used and the cultivation conditions. 6 The yeast Yarrowia lipolytica has been the most studied yeast for lipid production. [7][8][9][10] This yeast has been the subject of genetic and metabolic engineering, allowing researchers to obtain significant amounts of oil showing desirable profiles of PUFA.…”