Analysis and optimization of triacylglycerol synthesis in novel oleaginous Rhodococcus and Streptomyces strains isolated from desert soil

Röttig, Annika; Hauschild, Philippa; Madkour, Loutfy H.; Al-Ansari, Ahmed M.; Almakishah, Naief H.; Steinbüchel, Alexander

doi:10.1016/j.jbiotec.2016.03.040

Cited by 48 publications

(24 citation statements)

References 33 publications

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“…Although many streptomycetes are able to degrade soluble carboxymethyl cellulose and some can also degrade insoluble cellulose (40), this ability was not observed for Streptomyces strain G25 (15). The degradation of cellulose and uptake of the oligomers, such as cellotriose or cellobiose, were extensively studied in S. reticuli, which cleaves crystalline cellulose with a mycelium-associated cellulase, Cel1.…”

Section: Resultsmentioning

confidence: 99%

“…G25) ( Fig. 1) (15,43,44). BCAA are deaminated by BCAA transaminase (BCAT) (45), and the products (e.g., 2-keto-3-methylvaleric acid derived from isoleucine, as shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Lipids were extracted; separated via thin-layer chromatography (TLC) in n-hexane-diethyl ether-acetic acid (80:20:1, vol/ vol/vol) using approximately 40 g of oleyl oleate (WE), 20 g triolein (TAG), and 100 g oleic acid (free fatty acids [FFA]) as references (all purchased from Sigma-Aldrich); or quantified after methanolysis using gas chromatography (GC). TLC and GC analyses were performed as described before (15). Calibration curves were generated using commercially available fatty acids (C 10 , C 12 , C 14 , C 15 , anteiso-C 15 , C 16 , C 16:1 , iso-C 16 , C 17 , C 18 , or C 18:1 ).…”

Section: Methodsmentioning

confidence: 99%

“…TLC and GC analyses were performed as described before (15). Calibration curves were generated using commercially available fatty acids (C 10 , C 12 , C 14 , C 15 , anteiso-C 15 , C 16 , C 16:1 , iso-C 16 , C 17 , C 18 , or C 18:1 ). For other fatty acid species, which could not be assigned to one of those known retention times, a mean conversion factor of all available calibration curves was generated to estimate their quantity.…”

Section: Methodsmentioning

confidence: 99%

“…This lipid yield was achieved after 6 to 7 days of cultivation in mineral salts medium (MSM) containing a limited nitrogen concentration of 0.025% (wt/vol) NH 4 Cl and 1% (wt/ vol) cellobiose. As is common for streptomycetes, the accumulated fatty acids of strain G25 were mostly long-chain, branched fatty acids (e.g., anteiso-C 15 or iso-C 16 ) and palmitate. These lipids could serve as feedstock for the production of partly branchedchain biodiesel with improved cold-temperature performance and stability properties (15).…”

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confidence: 92%

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Role of Wax Ester Synthase/Acyl Coenzyme A:Diacylglycerol Acyltransferase in Oleaginous Streptomyces sp. Strain G25

Röttig

Strittmatter

Schauer

et al. 2016

Appl Environ Microbiol

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Recently, we isolated a novel Streptomyces strain which can accumulate extraordinarily large amounts of triacylglycerol (TAG) and consists of 64% fatty acids (dry weight) when cultivated with glucose and 50% fatty acids (dry weight) when cultivated with cellobiose. To identify putative gene products responsible for lipid storage and cellobiose utilization, we analyzed its draft genome sequence. A single gene encoding a wax ester synthase/acyl coenzyme A (CoA):diacylglycerol acyltransferase (WS/DGAT) was identified and heterologously expressed in Escherichia coli. The purified enzyme Atf G25 showed acyltransferase activity with C 12 -or C 16 -acyl-CoA, C 12 to C 18 alcohols, or dipalmitoyl glycerol. This acyltransferase exhibits 24% amino acid identity to the model enzyme AtfA from Acinetobacter baylyi but has high sequence similarities to WS/DGATs from other Streptomyces species. To investigate the impact of Atf G25 on lipid accumulation, the respective gene, atf G25 , was inactivated in Streptomyces sp. strain G25. However, cells of the insertion mutant still exhibited DGAT activity and were able to store TAG, albeit in lower quantities and at lower rates than the wild-type strain. These findings clearly indicate that Atf G25 has an important, but not exclusive, role in TAG biosynthesis in the novel Streptomyces isolate and suggest the presence of alternative metabolic pathways for lipid accumulation which are discussed in the present study. IMPORTANCEA novel Streptomyces strain was isolated from desert soil, which represents an extreme environment with high temperatures, frequent drought, and nutrient scarcity. We believe that these harsh conditions promoted the development of the capacity for this strain to accumulate extraordinarily large amounts of lipids. In this study, we present the analysis of its draft genome sequence with a special focus on enzymes potentially involved in its lipid storage. Furthermore, the activity and importance of the detected acyltransferase were studied. As discussed in this paper, and in contrast to many other bacteria, streptomycetes seem to possess a complex metabolic network to synthesize lipids, whereof crucial steps are still largely unknown. This paper therefore provides insights into a range of topics, including extremophile bacteria, the physiology of lipid accumulation, and the biotechnological production of bacterial lipids. Even extreme environments, such as arid, desert-like regions, are populated by prokaryotes. These mostly Gram-positive bacteria are subjected to extreme fluctuations of temperature and water supply. In addition to desiccation and the resulting cellular damage, the bacteria frequently encounter nutrient limitation. To withstand these harsh environmental conditions, the majority of bacteria have evolved various strategies and are able to store lipophilic compounds such as polyhydroxyalkanoates (PHA), triacylglycerols (TAG), or wax esters (WE) (1-3). TAG are synthesized as primary storage compounds by many actinomycetes-which represent the pre...

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Section: Resultsmentioning

confidence: 99%

“…G25) ( Fig. 1) (15,43,44). BCAA are deaminated by BCAA transaminase (BCAT) (45), and the products (e.g., 2-keto-3-methylvaleric acid derived from isoleucine, as shown in Fig.…”

Section: Resultsmentioning

confidence: 99%