Characterization, identification and application of lactic Acid bacteria isolated from forage paddy rice silage.

Kuikui Ni,Huili Pang,Dongxia Li,Yimin Cai,Yanping Wang,Daichang Yang

doi:10.1371/journal.pone.0121967

Abstract

There has been growing interest to develop forage rice as a new feed resource for livestock. This study was to characterize the natural population of lactic acid bacteria (LAB) and select potentially excellent strains for paddy rice silage preparation in China. One hundred and twenty-six strains were isolated and screened from paddy rice silage prepared using a small-scale fermentation system, and ninety-nine of these isolates were considered to be LAB based on their Gram-positive and catalase-negative morphology and the production of most of their metabolic products as lactic acid. These isolates were divided into eight groups (A-H) on the basis of their morphological and biochemical characteristics. The Group A to H strains were identified as Lactobacillus (L.) plantarum subsp. plantarum (species ratio: 8.1%), L. casei (5.1%), Leuconostoc (Ln.) pseudomesenteroides (11.1%), Pediococcus (P.) pentosaceus (24.2%), Enterococcus (E.) mundtii (12.1%), Lactococcus (Lc.) garvieae (15.2%), E. faecium (9.1%) and Lc. lactis subsp. lactis (15.2%) based on sequence analyses of their 16S rRNA and recA genes. P. pentosaceus was the most abundant member of the LAB population in the paddy rice silage. A selected strain, namely L. casei R 465, was found to be able to grow under low pH conditions and to improve the silage quality with low pH and a relatively high content of lactic acid. This study demonstrated that forage paddy rice silage contains abundant LAB species and its silage can be well preserved by inoculation with LAB, and that strain R 465 can be a potentially excellent inoculant for paddy rice silage.

Highlights

Paddy rice has been proven to be economically viable as a main dish for human consumption and as a forage crop for animals [1,2,3]
Lactic Acid Bacteria in Paddy Rice Silage growth in the demand for animal products has resulted in increased utilization of forage crops, such as paddy rice
All of the isolates were Gram-positive and catalase-negative bacteria, unable to grow at 50°C and able to grow at pH 4.0 to 7.0 (Table 1)

Summary

Introduction

Paddy rice has been proven to be economically viable as a main dish for human consumption and as a forage crop for animals [1,2,3]. With an increase in the population of China and improvements in the living standards, the resulting. Lactic Acid Bacteria in Paddy Rice Silage growth in the demand for animal products has resulted in increased utilization of forage crops, such as paddy rice. Well-preserved silages are dependent on appropriate fermentation after storage, which results in low pH and the production of sufficient acid to inhibit the growth of undesirable microorganisms [5,6]. The natural populations of LAB in fresh crops are often heterofermentative and low in number [8,9]. Homofermentative bacteria can be used to improve silage preservation by accelerating and enhancing the initial phase of the conservation process via the fermentation of water-soluble carbohydrates (WSC) into lactic acid with a subsequent rapid decrease in pH. To prevent the aerobic deterioration of silage, heterofermentative LAB species, such as L. brevis and L. buchneri, have been developed as silage additives [10]

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