Selection of Lactic Acid Bacteria for the Optimized Production of Sheep’s Milk Yogurt with a High Conjugated Linoleic Acid Content

Abstract

Thirty-five different lactic acid bacteria (LAB) strains were screened for their conjugated linoleic acid (CLA) isomers (C18:2 cis-9, trans-11 and C18:2 trans-10, cis-12) producing ability from linoleic acid (LA) in sheep's milk. Preliminary experiments revealed that Lactobacillus delbrüeckii ssp. bulgaricus 2230 and Streptococcus thermophilus St 360 among the screened strains had the highest CLA-producing ability. This two strains were assayed in an 11-run fractional factorial design to investigate the effect of four variables included glucose, powdered sheep milk, LA and inoculum ratio on CLA production in a sheep's milk yogurt. The optimum conditions for producing the highest levels of CLA (42.86%) were obtained by adding 10.00 mg/mL of glucose, 30.00 mg/mL of powdered sheep milk, 0.90 mg/mL of LA and a 1:2 (St:Lb) ratio of bacterial strains in the inoculum. This CLA-rich sheep's milk yogurt could be an important supplementary food source for increasing the CLA in the human diet.

Oleate Hydratase in Lactobacillus delbrueckii subsp. bulgaricus LBP UFSC 2230 Catalyzes the Reversible Conversion between Linoleic Acid and Ricinoleic Acid

“…bulgaricus LBP UFSC 2230 exceeded that of S. thermophilus strain 360, the LBP UFSC 2230 culture demonstrated the potential ability to synthesize the c 9, t 11-C 18:2 isomer, but the production of the t 10, c 12-C 18:2 was not observed. Nevertheless, in the opposite condition, there was a significant detection of the latter isomer ( 3 ).…”

“…It has previously been reported that L. delbrueckii subsp. bulgaricus LBP UFSC 2230 was the most efficient CLA producer among 13 strains of the same species ( 3 ). In the current study, we assessed the ability of OleH from L. delbrueckii subsp.…”

“… L. delbrueckii subsp. bulgaricus strain LBP UFSC 2230, isolated from Italian Grana Padano cheese, has been previously demonstrated to be the most efficient CLA producer among 13 strains of the same species tested ( 3 ). Reaction conditions included incubation of the inoculum in de Man-Rogosa-Sharpe (MRS) broth medium (Merck, Darmstadt, Germany) at 37°C for 18 h under anaerobic conditions.…”

“…Lactic acid bacteria (LAB) have extensively been used as microbial starter cultures for the fermentation of dairy products to promote health ( 1 ). These microorganisms act as cellular factories for the synthesis of secondary metabolites with functional properties, such as the production of conjugated linoleic acid (CLA) ( 2 – 5 ). CLA refers to a collective term describing a group of positional and geometric isomers of linoleic acid ( c 9, c 12-C 18:2 ; LA) with conjugated double bonds ( 6 ).…”

“…In a previous study, several LAB strains were screened for their ability to produce CLA from LA, and we found L. delbrueckii subsp. bulgaricus LBP UFSC 2230 as a potential strain to synthesize the c 9, t 11-C 18:2 isomer ( 3 ). The current study aimed to characterize the oleate hydratase (EC 4.2.1.53) enzyme from L. delbrueckii subsp.…”