Assistance in the update of the systematic literature review (SLR): 'Influence of copper on antibiotic resistance of gut microbiota on pigs (including piglets)'

A total of 901 references were examined to assess the influence of copper supplemented diets on copper and antibiotic resistance of gut microbiota in pigs (including piglets). Merely 33 references were found eligible to answer this review question. From these 33 references, eleven references were assigned as experimental field studies, ten references were experimental environmentally controlled studies, and twelve references were assigned as cross-sectional studies. The references assigned as experimental field studies provided the most suitable information for the review question. The other studies gave useful information concerning the mechanism of resistance or prevalence of resistant isolates. The overall methodological quality of the field studies was rather poor. Only three of the eleven field studies had a methodological quality that was considered acceptable for the present review question. Therefore, the restricted number of studies available from the SLR, and the limitations in terms of results and methodological quality do not allow excluding the possibility of a positive correlation between copper supplementation above requirements and development of antibiotic resistance

Microbial production of conjugated linoleic and linolenic acids in fermented foods: technological bottlenecks

Several food-grade bacteria are known to produce conjugated linoleic acid (CLA) and conjugated linolenic acid (CLNA) from linoleic acid (LA) and a-linolenic acid (ALA), respectively. Therefore, bifidobacteria and a Lactobacillus sakei strain, able to produce CLA and CLNA in vitro, were applied as starter cultures for the fermentation of milk and meat, respectively. However, for both the fermented milk and meat no increase in CLA and CLNA content was obtained. Although LA and ALA were present in sufficient amounts in milk, their availability as free fatty acids was likely too low. During meat fermentation, the prevailing temperature and pH conditions most probably were the limiting factors for conversion of LA and ALA

Bacterial production of conjugated linoleic and linolenic acid in foods: a technological challenge

Conjugated linoleic acid (CLA) and conjugated linolenic acid (CLNA) isomers are present in foods derived from ruminants as a result of the respective linoleic acid (LA) and -linolenic acid (LNA) metabolism by ruminal microorganisms and in animals' tissues. CLA and CLNA have isomer-specific, health-promoting properties, including anticarcinogenic, antiatherogenic, anti-inflammatory, and antidiabetic activity, as well as the ability to reduce body fat. Besides ruminal microorganisms, such as Butyrivibrio fibrisolvens, many food-grade bacteria, such as bifidobacteria, lactic acid bacteria (LAB), and propionibacteria, are able to convert LA and LNA to CLA and CLNA, respectively. Linoleate isomerase activity, responsible for this conversion, is strain-dependent and probably related to the ability of the producer strain to tolerate the toxic effects of LA and LNA. Since natural concentrations of CLA and CLNA in ruminal food products are relatively low to exert their health benefits, food-grade bacteria with linoleate isomerase activity could be used as starter or adjunct cultures to develop functional fermented dairy and meat products with increased levels of CLA and CLNA or included in fermented products as probiotic cultures. However, results obtained so far are below expectations due to technological bottlenecks. More research is needed to assess if bacterial production kinetics can be increased and can match food processing requirements

Linoleate isomerase activity occurs in lactic acid bacteria strains and is affected by pH and temperature

Aims: To investigate the ability of lactic acid bacteria (LAB) to convert linoleic acid (LA) and a-linolenic acid (alpha-LNA) to conjugated linoleic acid (CLA) and conjugated linolenic acid (CLNA), respectively. To assess pH and temperature influences on CLA and CLNA production by Lactobacillus sakei LMG 13558. Methods and Results: A screening of 48 LAB yielded one Lactobacillus curvatus, five Lactobacillus plantarum and four Lact. sakei strains displaying linoleate isomerase (LAI) activity. CLNA conversion percentages varied largely (1-60%). CLA conversion, occurring in three strains, was lower (2-5%). The LAI gene sequences of the ten LAI-positive strains shared 75-99% identity with the LAI gene sequence of a Lact. plantarum AS1.555. At pH 6.2, CLA and CLNA production by Lact. sakei LMG 13558 was higher at 30 degrees C than at 20 and 25 degrees C. At pH 5.5 (30 degrees C) or 37 degrees C (pH 6.2), LA was not converted and a-LNA only slightly converted. Conclusions: LAB show strain-dependent LAI activity. Production of CLA and CLNA is affected by pH and temperature, as shown for Lact. sakei LMG 13558. Significance and Impact of the Study: Several LAB produce CLA and/or CLNA, as shown for Lact. sakei and Lact. curvatus for the first time. These findings offer potential for the manufacturing of fermented functional foods

Production of conjugated linoleic acid and conjugated linolenic acid isomers by Bifidobacterium species

Conjugated linoleic acid (CLA) and conjugated linolenic acid (CLNA) isomers have attracted great interest because of their potential health benefits. Formation of CLA and CLNA takes place in the rumen during biohydrogenation. Several studies have indicated that certain types of intestinal bacteria, including bifidobacteria, are able to convert linoleic acid (LA) to CLA. The role of intestinal bacteria in the formation of CLNA isomers is largely unknown. In the present study, a screening of 36 different Bifidobacterium strains for their ability to produce CLA and CLNA from free LA and alpha-linolenic acid (LNA), respectively, was performed. The strains were grown in MRS broth, to which LA or LNA (0.5 mg ml(-1)) were added after 7 h of bacterial growth. Cultures were further incubated at 37A degrees C for 72 h. Six strains (four Bifidobacterium breve strains, a Bifidobacterium bifidum strain and a Bifidobacterium pseudolongum strain) were able to produce different CLA and CLNA isomers. Conversion percentages varied from 19.5% to 53.5% for CLA production and from 55.6% to 78.4% for CLNA production among these strains. The CLA isomers produced were further identified with Ag+-HPLC. LA was mainly converted to t9t11-CLA and c9t11-CLA. The main CLNA isomers were identified with GC-MS as c9t11c15-CLNA and t9t11c15-CLNA