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We focused on the production of docosahexaenoic acid (DHA)-containing microbial lipids by Aurantiochytriumsp. using of defatted soybean (DS) as a nitrogen source. Defatted soybean is a plant biomass that could provide a sustainable supply at a low cost. Results showed that Aurantiochytriumsp. could not directly assimilate the DS as a nitrogen source but could grow well in a medium containing DS fermented with rice malt. When cultivated in a fermented DS (FDS) medium, Aurantiochytriumsp. showed vigorous growth with the addition of sufficient sulfate and chloride ions as inorganic nutrients without seawater salt. A novel isolated Aurantiochytriumsp. 6-2 showed 15.8 ± 3.4 g/L DHA productivity (in 54.8 ± 12.1 g/L total fatty acid production) in 1 L of the FDS medium. Therefore, DHA produced by Aurantiochytriumsp. using FDS enables a stable and sustainable DHA supply and could be an alternative source of natural DHA derived from fish oil.Graphical AbstractFor the development of novel fish feed, docosahexaenoic acid (DHA) produced by a novel isolated strain Aurantiochytriumsp. 6-2 was applied as an alternative source of DHA by using defatted soybean treated with koji.

ω3 Polyunsaturated fatty acids are currently obtained mainly from fisheries; thus, sustainable alternative sources such as oleaginous microorganisms are required. Here, we describe the isolation, characterization, and application of 3 novel ω3 desaturases with ω3 polyunsaturated fatty acid–producing activity at ordinary temperatures (28 °C). First, we selected Pythium sulcatumand Plectospira myriandraafter screening for oomycetes with high eicosapentaenoic acid/arachidonic acid ratios and isolated the genes psulω3and pmd17, respectively, which encode ω3 desaturases. Subsequent characterization showed that PSULω3 exhibited ω3 desaturase activity on both C18 and C20 ω6 polyunsaturated fatty acids while PMD17 exhibited ω3 desaturase activity exclusively on C20 ω6 polyunsaturated fatty acids. Expression of psulω3and pmd17in the arachidonic acid–producer Mortierella alpinaresulted in transformants that produced eicosapentaenoic acid/total fatty acid values of 38% and 40%, respectively, at ordinary temperatures. These ω3 desaturases should facilitate the construction of sustainable ω3 polyunsaturated fatty acid sources.Graphical AbstractCharacterization of ω3 fatty acid desaturases from oomycetes and their application toward eicosapentaenoic acid production in Mortierella alpina.

ABSTRACTCyclooxygenases are responsible for the production of prostaglandin H2(PGH2) from arachidonic acid. PGH2can be converted into some bioactive prostaglandins, including prostaglandin F2α(PGF2α), a potent chemical messenger used as a biological regulator in the fields of obstetrics and gynecology. The chemical messenger PGF2αhas been industrially produced by chemical synthesis. To develop a biotechnological process, in which PGF2αcan be produced by a microorganism, we transformed an oleaginous fungus, Mortierella alpina1S-4, rich in triacylglycerol consisting of arachidonic acid using a cyclooxygenase gene from a red alga, Gracilaria vermiculophylla. PGF2αwas accumulated not only in the mycelia of the transformants but also in the extracellular medium. After 12 days of cultivation approximately 860 ng/g and 6421 µg/L of PGF2αwere accumulated in mycelia and the extracellular medium, respectively. The results could facilitate the development of novel fermentative methods for the production of prostanoids using an oleaginous fungus.

Nitrifying microbial consortia were enriched from bark compost in a water system by regulating the amounts of organic nitrogen compounds and by controlling the aeration conditions with addition of CaCO3for maintaining suitable pH. Repeated enrichment showed reproducible mineralization of organic nitrogen via the conversion of ammonium ions () and nitrite ions () into nitrate ions (). The change in microbial composition during the enrichment was investigated by PCR-DGGE analysis with a focus on prokaryote, ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, and eukaryote cell types. The microbial transition had a simple profile and showed clear relation to nitrogen ions transition. Nitrosomonasand Nitrobacterwere mainly detected during and oxidation, respectively. These results revealing representative microorganisms acting in each ammonification and nitrification stages will be valuable for the development of artificial simple microbial consortia for organic hydroponics that consisted of identified heterotrophs and autotrophic nitrifying bacteria.

The PUFAs include many bioactive lipids. The microbial metabolism of C18PUFAs is known to produce their bioactive isomers, such as conjugated FAs and hydroxy FAs, but there is little information on that of C20PUFAs. In this study, we aimed to obtain anaerobic bacteria with the ability to produce novel PUFAs from C20PUFAs. Through the screening of ∼100 strains of anaerobic bacteria, Clostridium bifermentansJCM 1386 was selected as a strain with the ability to saturate PUFAs during anaerobic cultivation. This strain converted arachidonic acid (cis-5,cis-8,cis-11,cis-14-eicosatetraenoic acid) and EPA (cis-5,cis-8,cis-11,cis-14,cis-17-EPA) into cis-5,cis-8,trans-13-eicosatrienoic acid and cis-5,cis-8,trans-13,cis-17-eicosatetraenoic acid, giving yields of 57% and 67% against the added PUFAs, respectively. This is the first report of the isolation of a bacterium transforming C20PUFAs into corresponding non-methylene-interrupted FAs. We further investigated the substrate specificity of the biohydrogenation by this strain and revealed that it can convert two cisdouble bonds at the ω6 and ω9 positions in various C18and C20PUFAs into a transdouble bond at the ω7 position. This study should serve to open up the development of novel potentially bioactive PUFAs.

Abstract: The ability to produce CLA from ricinoleic acid is widely distributed in lactic acid bacteria. Washed cells of Lactobacillus plantarum JCM 1551 were selected as a potential catalyst for CLA production from ricinoleic acid. Cells cultivated in medium supplemented with a mixture of α-linolenic acid and linoleic acid showed enhanced CLA productivity. Under optimal reaction conditions, with the free acid form of ricinoleic acid as the substrate and washed cells of L. plantarum as the catalyst, 2.4 mg/mL CLA was produced from 3.4 mg/mL ricinoleic acid in 90 h, with a molar yield with respect to ricinoleic acid of 71%. The CLA produced, which was obtained in the FFA form, consisted of a mixture of two CLA isomers, cis-9,trans-11-octadecadienoic acid (21% of total CLA) and trans-9,trans-11-octadecadienoic acid (79% of total CLA), and accounted for 72% of the total FA obtained.

The ability to produce CLA from ricinoleic acid is widely distributed in lactic acid bacteria. Washed cells of Lactobacillus plantarumJCM 1551 were selected as a potential catalyst for CLA production from ricinoleic acid. Cells cultivated in medium supplemented with a mixture of a-linolenic acid and linoleic acid showed enhanced CLA productivity. Under optimal reaction conditions, with the free acid form of ricinoleic acid as the substrate and washed cells of L. plantarumas the catalyst, 2.4 mg/mL CLA was produced from 3.4 mg/mL ricinoleic acid in 90 h, with a molar yield with respect to ricinoleic acid of 71%. The CLA produced, which was obtained in the FFA form, consisted of a mixture of two CLA isomers, cis-9,trans-11-octadecadienoic acid (21% of total CLA) and trans-9,trans-11-octadecadienoic acid (79% of total CLA), and accounted for 72% of the total FA obtained.

An isomer of the conjugated linoleic acid (CLA) produced from linoleic acid by Lactobacillus plantarumwas identified as cis-9,trans-11-octadecadienoic acid by proton nuclear magnetic resonance spectroscopy. Together with earlier results, we concluded that the bacterium produces two CLA isomers, cis-9,trans-11- and trans-9,trans-11-octadecadienoic acid from linoleic acid. The addition of L-serine, glucose, AgNO3, or NaCl to the reaction mixture reduced production of the latter.

Ricinoleic acid (12-hydroxy-cis-9-octadecaenoic acid) was an effective substrate for conjugated linoleic acid (CLA) production by washed cells of Lactobacillus plantarumAKU 1009a. The CLA produced was a mixture of cis-9,trans-11- and trans-9,trans-11-octadecadienoic acids. Addition of α-linolenic acid to the culture medium increased the CLA productivity of the washed cells. In the presence of lipase, castor oil, in which the main fatty acid component is ricinoleic acid, also was a substrate for CLA.