Abstract— The use of anaerobic digestate as fertilizer is considered beneficial since it provides plant nutrients and organic matter to soils. However, there is limited information about plant growth promoting bacteria (PGPB) in digestate. In this study, we isolated Bacillus and Pseudomonas from two types of anaerobic digestates, and selected three different plant growth promoting traits and antifungal activity to screen 200 bacteria isolated from each digestate. Then 6 isolates based on plant growth promoting traits were selected and inoculated with common wheat seeds to evaluate their plant growth promoting activity. Cultivable population of Bacillus and Pseudomonas were 2.20 × 106 and 6.98 × 104 CFU g-1 dry matter in mesophilic digestate, while were 6.86 × 105 and 5.65 × 104 CFU g-1 dry matter in thermophilic digestate. Twenty-five bacterial isolates from mesophilic digestate and 12 bacterial isolates from thermophilic digestate showed positive plant growth promoting traits or antifungal activity. In plant growth promoting assay, all isolates significantly promoted growth of wheat seedlings (p < 0.05). Seedlings stem length was increased from 28.5% to 38.6% by bacteria inoculation. In addition, bacteria inoculation increased seedlings stem weight from 113.3% to 214.2% and root weight from 108.6% to 207.2% as compared to un-inoculated control. The results showed that anaerobic digestate was a potential source for isolation of PGPB, and PGPB in digestate would be beneficial for plant growth with fertilizer application.
Keywords— Anaerobic digestate, Plant growth promoting bacteria (PGPB), Bacillus, Pseudomonas, Common wheat (Triticum aestivum).
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