Excessive input of fertilizer results in the accumulation of a large amount of salt in the soil, namely secondary salinization, especially nitrate, which decreases the quality and productivity of food.
Microbial remediation is an eco-friendly remediation method. However microbial activity is easily affected by soil temperature, humidity, pH and salinity. Seaweeds polysaccharides can stimulate microbial activity to achieve high remediation performance.
Recently, a research team led by Prof. LI Pengcheng from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS) has revealed how Enteromorpha linza polysaccharide (EP) promotes the growth and nitrate removal ability of Bacillus subtilis.
The study was published in International Journal of Biological Macromolecules on Apr. 18.
The researchers revealed the relationship between EP and Bacillus subtilis, which can transform nitrate. A sole carbon source experiment showed that Bacillus subtilis could utilize EP, and the bacterial density was maximally increased by 54.43% in the EP groups. The results of reducing sugar determination proved the secretion of polysaccharide-degrading enzymes.
Scanning electron microscopy showed that the EP groups had fewer spores and shrunken bacteria, indicating that EP could improve the growth environment and maintain bacterial integrity. Additionally, the ratios of periplasmic nitrate reductase, nitrite reductase, and dissimilatory nitrate reductase in the EP groups were maximally increased by 107.22%, 84.70% and 36.10%, respectively.
"By studying the growth-promoting mechanism, we clearly understand how seaweed polysaccharides stimulate microbial growth, which provides a theoretical basis for the efficient repair of functional microorganisms stimulated by active substances in the future and expands the screening range of microorganisms that can degrade algae polysaccharides," said ZHANG Hui, first author of the study.
"The mechanism of safe nitrogen removal indicated that the added substances could regulate the metabolic process of denitrifying microorganisms and effectively avoid defects in soil remediation, thus making it possible for denitrifying bacteria to be widely used in soil remediation," said Prof. LI.
