Natural lactic acid bacteria population of tropical grasses and their fermentation factor analysis of silage prepared with cellulase and inoculant

Natural lactic acid bacteria (LAB) populations in
tropical grasses and their fermentation characteristics
on silage prepared with cellulase enzyme and LAB inoculants
were studied. A commercial inoculant Lactobacillus
plantarum Chikuso 1 (CH), a local selected strain
Lactobacillus casei TH14 (TH14), and 2 cellulases,
Acremonium cellulase (AC) and Maicelase (MC; Meiji
Seika Pharma Co. Ltd., Tokyo, Japan), were used as
additives to silage preparation with fresh and wilted (6
h) Guinea grass and Napier grass. Silage was prepared
using a laboratory-scale fermentation system. Treatments
were CH, TH14, AC at 0.01% fresh matter, AC
0.1%, MC 0.01%, MC 0.1%, CH+AC 0.01%, CH+AC
0.1%, CH+MC 0.01%, CH+MC 0.1%, TH14+AC 0.1%,
TH14+AC 0.01%, TH14+MC 0.1%, and TH14+MC
0.01%. Microorganism counts of Guinea grass and
Napier grass before ensiling were 102 LAB and 106
aerobic bacteria; these increased during wilting. Based
on morphological and biochemical characteristics, and
16S rRNA gene sequence analysis, natural strains from
both grasses were identified as L. plantarum, L. casei,
Lactobacillus acidipiscis, Leuconostoc pseudomesenteroides,
Leuconostoc garlicum, Weissella confusa, and
Lactococcus lactis. Lactobacillus plantarum and L. casei
are the dominant species and could grow at lower pH
and produce more lactic acid than the other isolates.
Crude protein and neutral detergent fiber were 5.8 and
83.7% of dry matter (DM) for Guinea grass, and 7.5
and 77.1% of DM for Napier grass. Guinea grass had
a low level of water-soluble carbohydrates (0.39% of
DM). Guinea grass silage treated with cellulase had a
lower pH and higher lactic acid content than control
and LAB treatments. The 0.1% AC and MC treatments
had the best result for fermentation quality. All high
water-soluble carbohydrate (2.38% DM) Napier grass
silages showed good fermentation quality. Compared
with control and LAB-inoculated silage, the cellulasetreated
silages had significantly higher crude protein
content and lower neutral detergent fiber and acid detergent
fiber contents. The results confirmed that cellulase
could improve tropical silage quality, inhibiting
protein degradation and promoting fiber degradation.
Key words: cellulase, fermentation factor, lactic acid
bacteria, tropical silage