Production of cis-9,trans-11-conjugated linoleic acid in camelina meal and okara by an oat-assisted microbial process.

A method to obtain cis-9,trans-11-conjugated linoleic acid (c9,t11-CLA) into camelina meal and okara, the byproducts of plant oil processing, is described. The triacylglycerols in these materials were hydrolyzed with the aid of lipolytically active oat flour for 3 weeks at a water activity of 0.70. The resulting free linoleic acid was then isomerized predominantly to c9,t11-CLA by resting cells of Propionibacterium freudenreichii ssp. shermanii in 5% aqueous camelina meal and okara slurries. In camelina meal slurries, c9,t11-CLA content after 21 h of fermentation was 0.83 mg/mL and 96 mg/g of total lipids. In okara slurries, the content of c9,t11-CLA was 1.1 mg/mL and 78 mg/g of total lipids. Doubling the hydrolysis time in okara increased the subsequent content of c9,t11-CLA to 1.4 mg/mL, corresponding to 110 mg/g of total lipids. After isomerization, CLA was concentrated into a particulate material of the slurries by acidification. The results suggest that the method is applicable to a wide spectrum of lipid-containing plant materials to further increase their nutritional value.

Positional distribution of conjugated linoleic acid in triacylglycerol of Saccharomyces cerevisiae.

Saccharomyces cerevisiae was cultivated in the presence of cis-9,trans-11 or trans-10,cis-12 isomers of free conjugated linoleic acid (CLA), and the effects of the isomers on the regioisomerisms of triacylglycerol (TAG) of the yeast were elucidated. Both isomers constituted about 34% of all fatty acids and increased drastically the number of different TAG species. Nearly all of the species contained CLA in at least one sn-position. In the most abundant species analyzed (20% of total species), the cis-9,trans-11 isomer appeared in combination with monounsaturated fatty acids (C16:1, C:18:1) whereas trans-10,cis-12 isomer was most frequently present with a medium chain fatty acid (C10:0 or C12:0) in the sn-2 position and C16:0 in one of the end positions (14% of total species). With either isomer, the amount of TAG species in which CLA encompassed all sn-positions was ca. 4%. Thus, S. cerevisiae can be used to produce edible single cell oil characterized by very heterogeneous distribution of CLA among the different TAG species.

Microbially safe utilization of non-inactivated oats (Avena sativa L.) for production of conjugated linoleic acid.

A microbially safe process for the enrichment of conjugated linoleic acid (CLA) in oats was developed. The process consists of hydrolysis of oat lipids by non-inactivated oat flour, followed by propionibacterium-catalyzed isomerization of the resulting free linoleic acid to CLA. The first stage was performed at water activity (a(w)) 0.7, where hydrolysis of triacylglycerols progressed efficiently without growth of the indigenous microflora of flour. Thereafter, the flour was incubated as a 5% (w/v) aqueous, sterilized slurry with Propionibacterium freudenreichii ssp. shermanii. The amount of CLA produced in 20 h was 11.5 mg/g dry matter corresponding to 116 mg/g lipids or 0.57 mg/mL slurry. The oat flour had also the capability to hydrolyze exogenous oils at a(w) 0.7. Sunflower oil, added to increase linoleic acid content in triacylglycerols 2.7-fold, was hydrolyzed rapidly. Isomerization of this oil-supplemented flour as a 5% slurry gave final CLA content of 22.3 mg/g dry matter after 50 h of fermentation, corresponding to 118 mg/g lipids or 1.14 mg/mL slurry. Storage stability of CLA in fermented oat slurries at 4 degrees C was good.

Enrichment of conjugated linoleic acid in oats (Avena sativa L.) by microbial isomerization.

A method for microbial isomerization of oat linoleic acid to conjugated linoleic acid (CLA) was developed. The method includes hydrolysis of oat lipids in aqueous flour slurries by the endogenous oat lipase. Then, the flour slurry containing free linoleic acid is utilized as a substrate for the isomerization reaction carried out by resting cells of Propionibacterium freudenreichii ssp. shermanii. The isomerization reaction progressed most effectively when, after the lipid hydrolysis period, the pH of the slightly acidic oat slurry was elevated to 8.0-8.5 and maintained at this range. With slurries containing 5% (w/v) oat flour, the amounts of CLA formed per dry matter were up to 10.1 mg/g corresponding to 102 mg/g lipids or 0.44 mg/mL slurry. Increments in the flour content up to 15% increased the volumetric production of CLA to 0.85 mg/mL. The proportion of the cis-9,trans-11 isomer was 80% of the total CLA formed. CLA could be concentrated into the solid material of the oat slurry by acidification.