Diversity of Marine 1,3-Xylan-Utilizing Bacteria and Characters of Their Extracellular 1,3-Xylanases

Abstract

1,3-xylan is present in the cell walls of some red and green algae and is an important organic carbon in the ocean. However, information on its bacterial degradation is quite limited. Here, after enrichment with 1,3-xylan, the diversity of bacteria recovered from marine algae collected in Hainan, China, was analyzed with both the 16S rRNA gene amplicon sequencing and the culture-dependent method. Bacteria recovered were affiliated with more than 19 families mainly in phyla Proteobacteria and Bacteroidetes, suggesting a high bacterial diversity. Moreover, 12 strains with high 1,3-xylanase-secreting ability from genera Vibrio, Neiella, Alteromonas, and Gilvimarinus were isolated from the enrichment culture. The extracellular 1,3-xylanases secreted by Vibrio sp. EA2, Neiella sp. GA3, Alteromonas sp. CA13-2, and Gilvimarinus sp. HA3-2, which were taken as representatives due to their efficient utilization of 1,3-xylan for growth, were further characterized. The extracellular 1,3-xylanases secreted by these strains showed the highest activity at pH 6.0–7.0 and 30–40°C in 0–0.5M NaCl, exhibiting thermo-unstable and alkali-resistant characters. Their degradation products on 1,3-xylan were mainly 1,3-xylobiose and 1,3-xylotriose. This study reveals the diversity of marine bacteria involved in the degradation and utilization of 1,3-xylan, helpful in our understanding of the recycling of 1,3-xylan driven by bacteria in the ocean and the discovery of novel 1,3-xylanases.

Gilvimarinus xylanilyticus sp. nov., a novel 1,3-xylanase-secreting bacterium isolated from a marine green alga

“…Strain HB14 T was isolated from a green alga ( Chaetomorpha sp.) collected from a Caulerpa lentillifera aquaculture base in Wenchang, Hainan, China ( Sun et al, 2021 ). Strain G. chinensis CGMCC 1.7008 T was purchased from CGMCC and characterized alongside for comparative purposes.…”

“…1,3-xylan was prepared as previously described ( Sun et al, 2021 ). Growth of strain HB14 T on 1,3-xylan was determined at 30°C and pH 7.5 with 0.2% (w/v) 1,3-xylan as the sole carbon source by using 0.2% (w/v) xylose and glucose as the control substrates.…”

“…; Sun et al, 2021 ). Strain HB14 T was prominent by its low 16S rRNA gene sequence similarity (97.7%) to known species in the genus Gilvimarinus and its ability to secrete 1,3-xylanases on the plate containing 1,3-xylan ( Sun et al, 2021 ). In this study, the exact taxonomic position of strain HB14 T was determined by using a polyphasic approach.…”

“…1,3-xylan is a homopolymer composed of β-1,3-linked D-xylopyranose units, which is peculiar to marine algae and is the main component in the cell walls of some red and green algae ( Iriki et al, 1960 ; Veluraja and Atkins, 1987 ; Hsieh and Harris, 2019 ; Qeshmi et al, 2020 ). 1,3-xylan is considered the main xylan structure and an important organic carbon in the ocean ( Qeshmi et al, 2020 ; Sun et al, 2021 ). In addition, 1,3-xylan-containing algal biomass serves as a potential feedstock for producing useful chemical commodities and functional 1,3-xylooligosaccharides ( Goddard-Borger et al, 2012 ; Maeda et al, 2012 ; Umemoto et al, 2012 ).…”

“…During an investigation of 1,3-xylan-secreting bacteria from green algal samples collected from a Caulerpa lentillifera aquaculture base in Wenchang, Hainan, China, a strain, designated HB14 T , was isolated from a green alga ( Chaetomorpha sp. ; Sun et al, 2021 ). Strain HB14 T was prominent by its low 16S rRNA gene sequence similarity (97.7%) to known species in the genus Gilvimarinus and its ability to secrete 1,3-xylanases on the plate containing 1,3-xylan ( Sun et al, 2021 ).…”