Enzymatic characteristics of crude feruloyl and acetyl esterases of rumen fungus Neocallimastix sp. YAK11 isolated from yak (Bos grunniens)

Abstract

Summary Rumen fungus Neocallimastix sp. YAK11 was isolated from yak (Bos grunniens), and three consecutive 10‐day pure cultures were anaerobically performed at 39 °C in 20‐ml Hungate’s tubes to explore ferulic acid esterase (FAE) and acetyl esterase (AE) activity profiles of the fungus grown on whole hay fraction of Chinese wildrye grass (Leymus chinensis) (WHOcw, n = 4) and its neutral detergent fibre fraction (NDFcw, n = 4), respectively. An aliquot of 0.7‐ml culture was sampled daily using a sterile syringe, and 0.7‐ml fresh medium was immediately added to the tubes to compensate for the withdrawn samples. Peak esterase activity occurred for FAE on day 5 (p < 0.001) and for AE on day 6 (p < 0.001). The mean activities of FAE and AE in WHOcw were 2.07 and 1.29 times of those in NDFcw (p < 0.001). Both FAE and AE activities were positively correlated with xylanase (r > 0.65, p < 0.001) and carboxymethyl cellulase (r > 0.57, p < 0.001) activities. Total volatile fatty acid concentration was positively correlated with enzyme activities of AE (r > 0.87, p < 0.001), FAE (r > 0.82, p < 0.001) and xylanase (r > 0.56, p < 0.001). Crude enzyme solution was harvested for the fungus grown on WHOcw, and the pH optimum of FAE activity was 8.0 while the optimum for AE was 9.0. Both FAE and AE had a broad pH stability range. The optimal temperatures for FAE and AE activity were 40 and 50 °C. The Michaelis constant (Km) and maximum velocity (Vmax) for FAE against methyl ferulate at pH 6.0 and 39 °C were 0.078 mm and 2.93 mU, respectively. The Km and Vmax for AE against p‐nitrophenyl acetate at pH 7.0 and 39 °C were 2.73 mm and 666.67 mU, respectively. Both FAE and AE may have prospective advantages for the enzymatic degradation of roughages in ruminant animals.

Patterns and determinants of the global herbivorous mycobiome

“…Within the highly diverse microbial consortia residing in the expanded herbivorous alimentary tract, the anaerobic gut fungi (AGF, phylum Neocallimastigomycota) were the last to be recognized [8][9][10] and remain the most enigmatic. In spite of their critical role in initiating plant biomass colonization [11,12], their wide array of highly e cient lignocellulolytic enzymes [13][14][15][16][17][18][19][20][21][22], and their biotechnological potential [23][24][25], AGF diversity and distribution patterns remain, to-date, very poorly characterized [26]. Culture-independent efforts targeting AGF have long been hampered by the documented shortcomings of the universal fungal ITS1 barcoding marker for accurately characterizing AGF diversity [26,27] and, until recently, by the lack of clear thresholds and procedures for genus and species OTUs delineation [28].…”

The uniqueness and superiority of energy utilization in yaks compared with cattle in the highlands: A review

“…Isolation and culture of the unique strains of rumen microbes in yaks would also be beneficial for the production of industrialized enzymes. For example, feruloyl and acetyl esterase secreted by anaerobic rumen fungi isolated from yaks displays unique enzymatic characteristics ( Cao et al., 2013 ). Rumen fungi in yaks have also been shown to possess high fibrolytic activity ( Wei et al., 2016b ).…”

Patterns and determinants of the global herbivorous mycobiome

“…Within the highly diverse microbial consortia residing in the expanded herbivorous alimentary tract, the anaerobic gut fungi (AGF, phylum Neocallimastigomycota) were the last to be recognized [8][9][10] and remain the most enigmatic. In spite of their critical role in initiating plant biomass colonization [11,12], their wide array of highly efficient lignocellulolytic enzymes [13][14][15][16][17][18][19][20][21][22], and their biotechnological potential [23][24][25],…”

“…Within the highly diverse microbial consortia residing in the expanded herbivorous alimentary tract, the anaerobic gut fungi (AGF, phylum Neocallimastigomycota) were the last to be recognized [8-10] and remain the most enigmatic. In spite of their critical role in initiating plant biomass colonization [11, 12], their wide array of highly efficient lignocellulolytic enzymes [13-22], and their biotechnological potential [23-25], AGF diversity and distribution patterns remain, to-date, very poorly characterized [26]. Culture-independent efforts targeting AGF have long been hampered by the documented shortcomings of the universal fungal ITS1 barcoding marker for accurately characterizing AGF diversity [26, 27] and, until recently, by the lack of clear thresholds and procedures for genus and species OTUs delineation [28].…”