Isolation and characterization of lactic acid bacteria for use as silage additives

Abstract

Sixteen lactic acid bacterial strains were isolated from silage and cow dung samples, and characterized to identify their potential as silage additives. They were identified as the members of the genera Lactobacillus, Enterococcus, and Weissella, and clustered into nine groups based on the sequences of the genes for 16S rRNA, RNA polymerase alpha subunit, 60-kDa heat shock protein, and phenylalanyl-tRNA synthase alpha subunit. Among them, the three strains which were genetically similar to L. plantarum showed the fastest growth and pH decrease in MRS and rye extract media, the highest numbers of available carbohydrates, and the widest ranges of pH, temperature, and salinity for growth. In addition, they showed no amplified DNA products in the PCR examination targeting the genes for the production of biogenic amines, and the MRS media where they had been cultured showed relatively high inhibition effect against the growth of silage-spoiling microorganisms, including fungi, yeast, and clostridia. The results suggest that these strains are good candidates for silage additives. However, the rye extract media where the lactic acid bacteria had been cultured had no effect on or stimulated the growth of the silage-spoiling microorganisms, and the causes must be established for the practical use of the lactic acid bacteria as silage additives.

Effect of temperature on single- and mixed-strain fermentation of ruminant feeds

“…3). The decrease in pH may be attributed to the production of organic acids such as lactic acid, acetic acid, and propionic acid, as reported in previous feed fermentation studies [19,23]. The maintenance of a pH level of 4.3 can be explained by LAB utilization of sugars originating from hemicellulose breakdown, causing a decrease in pH [23].…”

“…It also stabilizes gastric and intestinal pH and increases animal weight gain by improving fiber digestibility [14][15][16][17]. It has been reported that probiotic feed reduces harmful microorganisms in the intestine, increases beneficial microorganisms by improving the gut microenvironment [12], enhances digestion and absorption of feed, and reduces odor emissions from manure [18,19]. Furthermore, S. cerevisiae has mycotoxin removal ability and can tolerate salivary and gastrointestinal environments [20].…”

“…L. plantarum, a lactic acid bacteria (LAB), is one of the best suited lactic acid-producing species for decreasing feedstock pH [23], and thus can be implemented for extending shelf-life and decreasing nutritional loss in feeds [19]. Moreover, LAB with high intestinal adhesiveness block attachment of harmful organisms to the gut and repress the growth of noxious bacteria through production of antibacterial proteins [7][8][9].…”

“…Temperature plays a critical role in fermentation, and thus, fermentation conditions should be changed according to the season. Currently, many studies on the types of microorganisms used in fermentation of feeds are ongoing, but studies on fermentation temperatures and duration are lacking [18,19,27]. Therefore, it is necessary to study culture temperature and time.…”