Abstract
A total of 59 lactic acid bacteria (LAB) strains were isolated from corn stover silage. According to phenotypic and chemotaxonomic characteristics, 16S ribosomal DNA (rDNA) sequences and recA gene polymerase chain reaction amplification, these LAB isolates were identified as five species: Lactobacillus (L.) plantarum subsp. plantarum, Pediococcus pentosaceus, Enterococcus mundtii, Weissella cibaria and Leuconostoc pseudomesenteroides, respectively. Those strains were also screened for antimicrobial activity using a dual-culture agar plate assay. Based on excluding the effects of organic acids and hydrogen peroxide, two L. plantarum subsp. plantarum strains ZZU 203 and 204, which strongly inhibited Salmonella enterica ATCC 43971T, Micrococcus luteus ATCC 4698T and Escherichia coli ATCC 11775T were selected for further research on sensitivity of the antimicrobial substance to heat, pH and protease. Cell-free culture supernatants of the two strains exhibited strong heat stability (60 min at 100°C), but the antimicrobial activity was eliminated after treatment at 121°C for 15 min. The antimicrobial substance remained active under acidic condition (pH 2.0 to 6.0), but became inactive under neutral and alkaline condition (pH 7.0 to 9.0). In addition, the antimicrobial activities of these two strains decreased remarkably after digestion by protease K. These results preliminarily suggest that the desirable antimicrobial activity of strains ZZU 203 and 204 is the result of the production of a bacteriocin-like substance, and these two strains with antimicrobial activity could be used as silage additives to inhibit proliferation of unwanted microorganism during ensiling and preserve nutrients of silage. The nature of the antimicrobial substances is being investigated in our laboratory.
Highlights
Corn (Zea mays L.) is one of the high and stable-yield crops in the world, and the stover still contains good nutrients suitable for livestock, 30% is generally incinerated in the corn field after corn cobs have been harvested
In order to comprehensively understand the change of microorganisms after ensiling, we investigated the numbers of 7 kinds of microorganisms: LAB, coliform bacteria, molds, yeasts, bacilli, aerobic bacteria and clostridia
The counts of LAB increased from 1.4×105 colony forming units (CFU)/g fresh matter (FM) to 2.4×106 CFU/g FM after 30 days of ensiling, while other microorganisms were reduced by different degrees, especially molds and clostridia, which were not detected after ensiling
Summary
Corn (Zea mays L.) is one of the high and stable-yield crops in the world, and the stover still contains good nutrients suitable for livestock, 30% is generally incinerated in the corn field after corn cobs have been harvested. Certain LAB strains can be used as probiotics for animals, because of the production of lactic acid, but other compounds, such as bacteriocins and bacteriocin-like substances (BLS) (Todorov et al, 2011) are produced. Different from antibiotics, bacteriocins produced by LAB are generally recognized as safe substances, they are ribosomal synthesized and become inactivated by digestive proteases (Riley, 2009; Hellal et al, 2012) Because of their potential use as non-toxic and safe additives for food preservation, bacteriocins from LAB have attracted increased attention (Hata et al, 2010). To the best of our knowledge, this is the first report describing the isolation of LAB with antimicrobial activity from corn stover silage, and investigating their characteristic for their further application in feed additives
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
