CLA-enriched milk powder reverses hypercholesterolemic risk factors in hamsters

Modulating Heterologous Pathways and Optimizing Culture Conditions for Biosynthesis of trans-10, cis-12 Conjugated Linoleic Acid in Yarrowia lipolytica

A novel recombinant strain has been constructed for converting glycerol into a specific conjugated linoleic acid isomer (trans-10, cis-12 CLA) using Yarrowia lipolytica as host. The lipid accumulation pathway was modified for increasing lipid content. Overexpression of the diacylglycerol transferase (DGA1) gene improved the intracellular lipid yield by approximately 45% as compared to the original strain. The corresponding intracellular lipid yield of recombinant strain WXYL037 reached 52.2% of the cell dry weight. In combination with integration of Δ12 desaturase from Mortierella alpina (MA12D) and DGA1, the linoleic acid (LA) production content reached 0.88 g/L, which was 2-fold that of the original strain. Furthermore, with overexpressed DGA1, MA12D and Propionibacterium acnes isomerase (PAI), the titer of trans-10, cis-12 CLA in WXYL037 reached 110.6 mg/L after 72 h of shake flask culture, representing a 201.8% improvement when compared with that attained in the WXYL030 strain, which manifested overexpressed PAI. With optimal medium, the maximum CLA content and lipid yield of Y. lipolytica Po1g were 132.6 mg/L and 2.58 g/L, respectively. This is the first report of the production of trans-10, cis-12 CLA by the oleaginous yeast Y. lipolytica using glycerol as the sole carbon source through expression of DGA1 combined with MA12D and PAI.

Microbial Production of Conjugated Linoleic Acid and Conjugated Linolenic Acid Relies on a Multienzymatic System

Conjugated linoleic acids (CLAs) and conjugated linolenic acids (CLNAs) have gained significant attention due to their anticarcinogenic and lipid/energy metabolism-modulatory effects. However, their concentration in foodstuffs is insufficient for any therapeutic application to be implemented. From a biotechnological standpoint, microbial production of these conjugated fatty acids (CFAs) has been explored as an alternative, and strains of the genera Propionibacterium, Lactobacillus, and Bifidobacterium have shown promising producing capacities. Current screening research works are generally based on direct analytical determination of production capacity (e.g., trial and error), representing an important bottleneck in these studies. This review aims to summarize the available information regarding identified genes and proteins involved in CLA/CLNA production by these groups of bacteria and, consequently, the possible enzymatic reactions behind such metabolic processes. Linoleate isomerase (LAI) was the first enzyme to be described to be involved in the microbiological transformation of linoleic acids (LAs) and linolenic acids (LNAs) into CFA isomers. Thus, the availability of lai gene sequences has allowed the development of genetic screening tools. Nevertheless, several studies have reported that LAIs have significant homology with myosin-cross-reactive antigen (MCRA) proteins, which are involved in the synthesis of hydroxy fatty acids, as shown by hydratase activity. Furthermore, it has been suggested that CLA and/or CLNA production results from a stress response performed by the activation of more than one gene in a multiple-step reaction. Studies on CFA biochemical pathways are essential to understand and characterize the metabolic mechanism behind this process, unraveling all the gene products that may be involved. As some of these bacteria have shown modulation of lipid metabolism in vivo, further research to be focused on this topic may help us to understand the role of the gut microbiota in human health.

Absorption Kinetics of the Main Conjugated Linoleic Acid Isomers in Commercial-Rich Oil after Oral Administration in Rats

This study aimed to assess the oral absorption and plasma kinetics of two main isomers contained in commercial conjugated linoleic acid (CLA)-rich oil (Tonalin TG-80), rumenic acid (RA), and C18:2 trans-10, cis-12. The isomer plasma disposition after the single oral dose of 3000 mg of Tonalin TG-80/kg, containing 1200 mg/kg of each isomer, was studied in rats. The isomer plasma concentrations were determined by gas chromatography with flame ionization detection. The plasma kinetics showed rapid oral absorption of RA and C18:2 trans-10, cis-12 (t_1/2a 0.34 ± 0.09 and 0.53 ± 0.01 h) and slow elimination (t_1/2β 25.68 ± 3.29 and 18.12 ± 1.71 h); the maximal isomer plasma concentrations (C_max) of 8.48 ± 0.98 and 7.67 ± 0.80 μg mL^-1, respectively, were estimated at 2.08 ± 0.14 and 2.26 ± 0.11 h. Our results from a preclinical kinetic study in rats help to design future studies in humans for evaluating the CLA isomer dose-response.