Screening and evaluation of the ruminal cellulolytic bacteria and their potential application as probiotics.

Background and Objectives: Rumen microbiologists are looking for new probiotics to improve the digestibility of livestock diets. This study intended to screen and evaluate the ruminal cellulolytic bacteria (CBs) and their potential application as probiotics. Materials and Methods: Microbial culture and molecular techniques performed to isolate CBs from the rumen of camels, deer and rams. Their antibacterial and antibiogram tests were done using disc diffusion method. Their potential to degrade cellulose, starch, tannin and protein were investigated using clear zone halo, and spectrophotometric techniques. Bilious, saline, and acidic broth media were used to study the resistance of isolates in intestinal conditions. Results: The phylogenetic analysis revealed that the strains belonged to Firmicutes and Proteobacteria phyla, Citrobacter murliniae, Ornithinibacillus bavariensis, C. braakii, and Bacillus subtilis. The highest cellulase (CAS) activity was recorded by C. murliniae Dez wildlife13A (2.98 UmL-1), whereas C. braakii Loot desert 111A (1.14 Uml-1) was produced the lowest enzyme. The isolates were highly resistant to synthetic conditions of intestine (pH 2.5-3.5, bile 0.3-2%), as well as tolerated higher concentrations of NaCl (up to 10%). They effectively inhibited standard pathogen strains, and showed sensitivity to the used antibiotics. Conclusion: This study reports the cellulolytic O. bavariensis Tabbas desert 32A for the first time from the rumen, which will have potential biotechnological applications.

Screening the Rumen of Balochi Camel (Camelus dromedarius) and Cashmere Goat (Capra hircus) to Isolate Enzyme-Producing Bacteria as Potential Additives for Animal Feed.

Rumen microbiology has made a significant contribution to the discovery of biodegradation processes, which convert nutrients into energy for ruminants. Therefore, understanding the enzymatic potential in the rumen of different animal species is essential for developing efficient microbial feed additives. The aim of this study was to isolate enzyme-producing bacteria (EPBs) from the rumen of the Balochi camel (Camelus dromedarius) and Cashmere goat (Capra hircus) as potential additives for animal feed. The EPBs were screened based on the hydrolysis of carboxyl methyl cellulose, tannin, starch, and bovine serum albumin. The isolates were then subjected to enzyme activity assays and molecular characterization. Additionally, they were evaluated for their antagonistic effects, antibiotic susceptibility, and growth in acidic, bile, and saline media. Thirteen enzyme-producing strains were identified in the rumen of the camels and goats, belonging to the genera Klebsiella, Escherichia, Raoultella, Enterobacter and Pectobacterium. The highest and lowest tannase activities were recorded for Escherichia coli GHMGHE41 (10.46 Um/l-1) and Raoultella planticola GHMGHE15 (1.83 Um/l-1), respectively. Enterobacter cloacae GHMGHE18 (2.03 U/ml) was the most effective cellulolytic isolate, compared to Klebsiella strains (1.05 Um/l-1). The highest protease producer was Klebsiella pneumoniae GHMGHE13 (3.00 U/ml-1), while Escherichia coli GHMGHE17 (1.13 U/ml-1) had the lowest activity. Klebsiella pneumoniae GHMGHE13 (1.55 U/ml-1) and Enterobacter cloacae GHMGHE19 (1.26 U/ml-1) were the highest and lowest producers of amylase, respectively. The strains exhibited mixed responses to antibiotics and remained stable under stressful conditions. These findings indicate that ruminal EPBs have the potential to be used in animal feed, pending further in vivo studies.