AUTHOR=Xie Junjie , Yin Doudou , Ou Junchao , Lu Bo , Liao Siming , Yang Dengfeng , Zhang Hongyan , Shen Naikun 

TITLE=A new strain of Rhodococcus indonesiensis T22.7.1T and its functional potential for deacetylation of chitin and chitooligsaccharides

JOURNAL=Frontiers in Microbiology

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1427143

DOI=10.3389/fmicb.2024.1427143

ISSN=1664-302X

ABSTRACT=<sec id="sec1001"><title>Introduction</title><p>Chitin, abundant in marine environments, presents significant challenges in terms of transformation and utilization. A strain, T22.7.1<sup>T</sup>, with notable chitin deacetylation capabilities, was isolated from the rhizosphere of <italic>Acanthus ebracteatus</italic> in the North Sea of China. Comparative 16S rDNA sequence analysis showed that the new isolate had the highest sequence similarity (99.79%) with <italic>Rhodococcus indonesiensis</italic> CSLK01-03<sup>T</sup>, followed by <italic>R. ruber</italic> DSM 43338<sup>T</sup>, <italic>R. electrodiphilus</italic> JC435<sup>T</sup>, and <italic>R. aetherivorans</italic> 10bc312<sup>T</sup> (98.97%, 98.81%, and 98.83%, respectively). Subsequent genome sequencing and phylogenetic analysis confirmed that strain T22.7.1<sup>T</sup> belongs to the <italic>R. indonesiensis</italic> species. However, additional taxonomic characterization identified strain T22.7.1<sup>T</sup> as a novel type strain of <italic>R. indonesiensis</italic> distinct from CSLK01-03<sup>T</sup>.</p></sec><sec id="sec2001"><title>Methods</title><p>This study refines the taxonomic description of <italic>R. indonesiensis</italic> and investigates its application in converting chitin into chitosan. The chitin deacetylase (<italic>Ri</italic>CDA) activity of strain T22.7.1<sup>T</sup> was optimized, and the enzyme was isolated and purified from the fermentation products.</p></sec><sec id="sec3001"><title>Results</title><p>Through optimization, the <italic>Ri</italic>CDA activity of strain T22.7.1<sup>T</sup> reached 287.02 U/mL, which is 34.88 times greater than the original enzyme’s activity (8.0 U/mL). The natural CDA enzyme was purified with a purification factor of 31.83, and the specific activity of the enzyme solution reached 1200.33 U/mg. <italic>Ri</italic>CDA exhibited good pH and temperature adaptability and stability, along with a wide range of substrate adaptabilities, effectively deacetylating chitin, chitooligosaccharides, N-acetylglucosamine, and other substrates.</p></sec><sec id="sec4001"><title>Discussion</title><p>Product analysis revealed that <italic>Ri</italic>CDA treatment increased the deacetylation degree (DD) of natural chitin to 83%, surpassing that of commercial chitosan. Therefore, <italic>Ri</italic>CDA demonstrates significant potential as an efficient deacetylation tool for natural chitin and chitooligosaccharides, highlighting its applicability in the biorefining of natural polysaccharides.</p></sec>