Lactic acid producing bacteria for use in the exploitation of seaweeds

Shobarani, Halami and Sachindra (2012) set out to determine if fermentation by marine lacticacid producing bacteria (LAB) can be used as a viable method to extract bioactive molecules from seaweeds, in particular Sargassum sp. It has been well documented that marine algae contain many biologically active compounds which pharmalogical and therapeutic uses. While these algae have been exploited extensively current methods used for extraction, while effective, are often expensive and complex. Shobarani et al (2012) examined the effect of bioactive molecule extraction using LAB fermentation of Sargassum sp. , on blood coagulation and the antioxidant capabilities.

The algae samples were collected from the west coast of India. After collection samples were thoroughly washed, dried and milled. Bacterial communities were selected from samples taken from the water column, sediments and seaweeds. Bacterial samples were plated on MRS agar containing Sargassum powder as a substitute for glucose, and bromocresol as indicator of lactic acid production. Using several characteristics LAB were selected and identified using 16S RNA sequencing, resulting in the use of four different bacterial strains for testing. 

To determine the fermentation of the Sargassum powder, a broth was made containing 1% powder. This broth was inoculated at a concentration of 10⁵ CFU ml^-1 and incubated for 18 days. At regular intervals viable cell count, pH, total titratable acidity and presence of sugars was measured. For the anticoagulation assays Shobarani et al (2012) preformed two assays, an APTT assay and PT. Multiple antioxidant assays were preformed to determine factors as reducing potential, metal chelation, DPPH scavenging, nitric oxide scavenging, hydrogen peroxide scavenging, ABTS scavenging and oxygen quenching. 

The results showed that during the fermentation process the viability of the cultures increased up to 12 days of incubation, and further incubation showed a further decrease in cell count. During the incubation period a significant decrease in pH was observed, this occurred together with a steady increase in lactic acid content with an optimum concentration after 12 days. Together with the increase in bacterial cell count an increase in total sugars present in the broth.  

 Two blood coagulation assays were preformed to determine which inhibition pathway would be affected, APTT assay for the intrinsic pathway and PT assay for the extrinsic pathway. For the assays the samples were used that had been incubated for the optimum of 12 days. Results showed that the all samples in the APTT assays showed higher activity compared to the PT assays and control samples, suggesting that the algae extract inhibits the intrinsic coagulation cascade. During the antioxidant assays it was noted that on average antioxidant capabilities were increased compared to control samples. A significant correlation was found between the polyphenol content of the sample and the antioxidant capabilities, with polyphenol content increasing during the fermentation period.

Overall it was suggested that, using a controlled microbial flora, can be used as a viable alternative for other bioactive molecule extraction methods and natural fermentation. As all samples showed an increase in anticoagulation activity and antioxidant capabilities. Shobarani et al. (2012) find that this study provides a basis for the application of well-characterised and controlled LAB cultures in the production of functional foods, and with further study may also be used to develop a cheap and effective method to extract and purify bioactive molecules, and possibly help in determining the functional mechanisms of these molecules for therapeutic uses. 

Shobharani P., Halami, P., M., Sachindra, N., M.. (2012). Potential of marine lactic acid bacteria to ferment Sargassum sp. for enhanced anticoagulant and antioxidant properties . Journal of Applied Microbiology. 114 (1), 96-107.