Isolation, characterization and identification of pericarp-degrading bacteria for the production of off-odour-free white pepper from fresh berries of Piper nigrum L.

Abstract

To isolate, fermentatively evaluate and identify black pepper (Piper nigrum L.)-associated bacteria for the microbial decortication of fresh ripened berries and dried black pepper for preparation of off-odour-free white pepper. Among 45 bacterial isolates obtained from black pepper, seven of them were found to decorticate black pepper (>60%) and fresh pepper berries (98-100%) into white pepper within 5days of immersion in bacterial suspension. The 16S rRNA genes (1500-bp amplicon) of these bacteria were sequenced, and species identity was established by closest match in GenBank. Superior-quality white pepper was obtained with Bacillus subtilis (IISR WP 33, 34, 38), Bacillus licheniformis (IISR WP 43), Acinetobacter baumanii (IISR WP 35), Klebsiella pneumoniae (IISR WP 19) and Microbacterium barkeri (IISR WP25). The bacterial isolates were found to secrete multiple hydrolytic enzymes such as cellulase, pectinase, amylase, protease and xylanase. Bacterial cultures were deposited with International Depository Authority at Microbial Type Culture Collection, India, as patent deposits as prescribed in Budapest Treaty for microbial deposits. The white pepper, thus obtained from bacterial decortication process, was free from off-odour compound, especially skatole. Other biochemical constituents such as oleoresin, piperine and essential oils were found in the acceptable range. The bacterial decortication did not affect inherent constituents of pepper such as essential oil constituents, oleoresin and piperine content. One of the most significant findings of the work is identification of specific bacterial species for decortication of fresh berries or black pepper berries into value-added white pepper. This work paved way for developing a technological process for microbial decortication of fresh/black pepper for the production of superior-quality white pepper.