Characterization and probiotic potential of thermotolerant lactic acid bacteria from silage for ensiling crop residues

Abstract

Paddy straw, though abundantly available in India, is often burnt in fields, despite its potential as valuable feed resource for livestock. Ensiling provides a practical solution for its utilization, but challenges like low moisture, high fibre content, and unfavourable climatic conditions limit its effectiveness. In recent times, microbial-based approaches, particularly involving lactic acid bacteria (LAB), have shown promise in improving silage quality. However, suitable thermotolerant LAB strains that can perform under Indian field conditions remain unexplored. To address this, 45 Gram-positive, catalase-negative, and vancomycin-resistant LAB were isolated from naturally fermented silage collected from hot and humid regions of the country. Genus-specific 16S rRNA PCR confirmed all isolates as Lactobacilli and out of these, 35 were acid-tolerant, 26 bile-tolerant, and 12 could grow at 47–50 °C. RSB7 showed the maximum growth at elevated temperatures. Among thermotolerant cultures, six each were identified as homofermentative and heterofermentative, and were preserved in the National Collection of Dairy Cultures. RSB13 showed the highest hydrophobicity. RSB2 had superior co-aggregation and antioxidant activity, while RSB9 exhibited strong autoaggregation, ferulic acid esterase activity, and in vitro straw degradability. All isolates were non-hemolytic, non-mucinolytic, and antibiotic-sensitive. These thermotolerant Lactobacillus spp. showed good potential as safe and functional silage inoculants suitable for tropical Indian conditions.