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

Advances in research on microbial conjugated linoleic acid bioconversion

Conjugated linoleic acid (CLA) is a functional food ingredient with prebiotic properties that provides health benefits for various human pathologies and disorders. However, limited natural CLA sources in animals and plants have led microorganisms like Lactobacillus and Bifidobacterium to emerge as new CLA sources. Microbial conversion of linoleic acid to CLA is mediated by linoleic acid isomerase and multicomponent enzymatic systems, with CLA production efficiency dependent on microbial species and strains. Additionally, complex factors like LA concentration, growth status, culture substrates, precursor type, prebiotic additives, and co-cultured microbe identity strongly influence CLA production and isomer composition. This review summarizes advances in the past decade regarding microbial CLA production, including bacteria and fungi. We highlight CLA production and potential regulatory mechanisms and discuss using microorganisms to enhance CLA content and nutritional value of fermented products. We also identify primary microbial CLA production bottlenecks and provide strategies to address these challenges and enhance production through functional gene and enzyme mining and downstream processing. This review aims to provide a reference for microbial CLA production and broaden the understanding of the potential probiotic role of microbial CLA producers.

Production of conjugated linoleic acid by lactic acid bacteria; important factors and optimum conditions

Conjugated linoleic acid (CLA) has recently attracted significant attention as a health-promoting compound. CLA is a group of positional isomers of linoleic acid (LA) with a conjugated double bond naturally occurring in dairy and ruminant meat products. Microbial biosynthesis of CLA is a practical approach for commercial production due to its high safety and purity. There are some factors for the microbial CLA production such as strain type, microbial growth phase, pH, temperature and incubation time, based on which the amount and type of CLA can be controlled. Understanding the interplay of these factors is essential in optimizing the quantity and composition of microbial CLA, as discussed in the current study. Further exploration of CLA and its influences on human health remains a dynamic and evolving area of study.

Effect of Rosemary (Rosmarinus officinalis L.) Supplementation on Probiotic Yoghurt: Physicochemical Properties, Microbial Content, and Sensory Attributes

Rosemary (Rosmarinus officinalis L.) is a natural aromatic plant that belongs to the family of Lamiaceae. The rosemary plant has been utilized to preserve food due to its ability to prevent oxidation and microbial contamination. This study aimed to investigate the effect of fortifying yoghurt with rosemary extracts and probiotic bacteria (LAB) (Bifidobacterium longum ATCC15707 and two lactic acid bacteria, Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus) on its chemical composition, total phenolic compounds, antioxidant capacity, and sensory properties. The study results revealed significant differences in the total solids, protein, and ash content when rosemary concentration increased beyond 2%. However, there were no significant differences among the treatments in acidity and pH value. The sensory evaluation results indicated that the addition of aqueous extract of rosemary affected the sensory properties of yoghurt (flavour, body and texture, appearance, and overall grade), wherein an increasing concentration of rosemary extract increased score of flavour, body and texture, appearance, and overall grade. On the other hand, rosemary extract did not affect the sensory properties and chemical composition. To sum up, it can be stated that rosemary was used in the preparation of yoghurt with increased health benefits, acceptable sensory attributes, and the production of synbiotic yogurt.

Utilization of optimized processing conditions for high yield synthesis of conjugated linoleic acid by L. plantarum AB20-961 and L. plantarum DSM2601 in semi-dry fermented sausage

The aim of this study was to utilize optimized processing conditions to obtain the highest conjugated linoleic acid (CLA) contents in semi-dry fermented sausages produced with L. plantarum AB20-961 and L. plantarum DSM 2601. Optimized conditions were 5.7 meat pH, 5% hydrolyzed safflower oil addition, 10⁸ CFU/g added starter culture, fermentation time of 73 h for L. plantarum DSM2601 and 79 h for L. plantarum AB20-961, 24 °C fermentation temperature, 65 °C internal cooking temperature and 90% relative humidity. Results indicated that CLA contents in sausages were increased 21% by L. plantarum AB20-961 and 121% by L. plantarum DSM2601 after fermentation compared to initial CLA level determined on manufacturing day (P < .05). After fermentation, an increased CLA content of sausages remained stable during heat processing and storage. Sausages incorporated with L. plantarum strains and hydrolyzed safflower oil had the highest TBARS and PUFA levels, and the lowest pH and moisture content (P < .05). Differences were not found in sensorial and other physicochemical properties among sausage treatment groups. This study demonstrated that high CLA content can be achieved in sausages by utilizing optimum processing conditions described above and starter cultures (L. plantarum AB20-961 and L. plantarum DSM2601) without any adverse effects on quality of the final product.

Conjugated linoleic acid producing potential of lactobacilli isolated from goat (AXB) rumen fluid samples

OBJECTIVE

The present investigation was aimed to explore the potential of lactobacilli for conjugated linoleic acid (CLA) production, isolated from rumen fluid samples of lactating goats.

METHODS

A total of 64 isolates of lactobacilli were obtained using deMan-Rogosa-Sharpe (MRS) agar from rumen fluid of goats and further subjected to morphological and biochemical characterizations. Isolates found as gram-positive, catalase negative rods were presumptively identified as Lactobacillus species and further confirmed by genus specific polymerase chain reaction (PCR). The phylogenetic tree was constructed from the nucleotide sequences using MEGA6.

RESULTS

Out of the 64 isolates, 23 isolates were observed positive for CLA production by linoleate isomerase gene-based amplification and quantitatively by UV-spectrophotometric assay for the conversion of linoleic acid to CLA as well as gas chromatography-based assay. In all Lactobacillus species cis9, trans11 isomer was observed as the most predominant CLA isomer. These positive isolates were identified by 16S rRNA gene-based PCR sequencing and identified to be different species of L. ingluviei (2), L.salivarius (2), L. curvatus (15), and L. sakei (4).

CONCLUSION

The findings of the present study concluded that lactic acid bacteria isolated from ruminal fluid samples of goat have the potential to produce bioactive CLA and may be applied as a direct fed microbial to enhance the nutraceutical value of animal food products.

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.

A review of phytochemistry, metabolite changes, and medicinal uses of the common sunflower seed and sprouts (Helianthus annuus L.)

The sunflower (Helianthus annuus L.) seed and sprout is a ubiquitous crop with abundant nutrients and biological activities. This review summarizes the nutritional and medical importance currently recognized but under-researched concerning both seed and sprout highlighting the potential benefits of their phytochemical constituents including phenolic acids, flavonoids and tocopherols. Furthermore, the dynamic metabolite changes which occur during germination and biological activities are evaluated. The aim is to provide scientific evidence for improving the dietary and pharmaceutical applications of this common but popular crop as a functional food.

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 α-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.

Screening of Lactobacillus strains for their ability to produce conjugated linoleic acid in milk and to adhere to the intestinal tract

Conjugated linoleic acid (CLA) has been shown to provide beneficial effects on health; however, the amount consumed in food is far from that required for the desired effects. Thus, increasing the CLA content in dairy foods through milk fermentation with specific lactic acid bacteria (LAB) offers an interesting alternative. Moreover, some LAB may be able to adhere to the intestinal mucosa and produce CLA through endogenous synthesis. Therefore, the objective of this study was to screen LAB isolates for their ability to produce CLA in skim milk and in simulated gastrointestinal conditions. Additionally, the ability of selected CLA-producing LAB to adhere to the intestinal mucosa in a murine model was assessed. Results showed that of 13 strains of Lactobacillus tested, only 4 were able to produce CLA in skim milk supplemented with linoleic acid (13.44 ± 0.78 to 50.9 ± 0.26 µg/mL). Furthermore, these 4 Lactobacillus strains were able to survive and produce CLA in simulated gastrointestinal conditions and to adhere to the intestinal mucosa of Wistar rats after 7 d of oral inoculation with fluorescently labeled bacteria. Accordingly, these 4 Lactobacillus strains may be used to manufacture fermented dairy foods to increase CLA content, and consumption of these fermented milks may result in CLA produced endogenously by these LAB.

Production of conjugated linoleic and conjugated α-linolenic acid in a reconstituted skim milk-based medium by bifidobacterial strains isolated from human breast milk

Eight bifidobacterial strains isolated from human breast milk have been tested for their abilities to convert linoleic acid (LA) and α-linolenic acid (LNA) to conjugated linoleic acid (CLA) and conjugated α-linolenic acid (CLNA), respectively. These bioactive lipids display important properties that may contribute to the maintenance and improvement human health. Three selected Bifidobacterium breve strains produced CLA from LA and CLNA from LNA in MRS (160–170 and 210–230 μg mL⁻¹, resp.) and, also, in reconstituted skim milk (75–95 and 210–244 μg mL⁻¹, resp.). These bifidobacterial strains were also able to simultaneously produce both CLA (90–105 μg mL⁻¹) and CLNA (290–320 μg mL⁻¹) in reconstituted skim milk. Globally, our findings suggest that these bifidobacterial strains are potential candidates for the design of new fermented dairy products naturally containing very high concentrations of these bioactive lipids. To our knowledge, this is the first study describing CLNA production and coproduction of CLA and CLNA by Bifidobacterium breve strains isolated from human milk in reconstituted skim milk.