Isolation and characterization of effective microorganisms from palm oil sludge for enhancement of spent bio-adsorbents from aquaculture wastewater treatment

Abstract

A total of 4 bacterial (Bacillus sp., Bacillus pumilus, Pseudomonas tuomuerensis, and Pseudomonas aeruginosa) and 2 fungal (Talaromyces oumae-annae and Meira sp.) isolates were discovered to have high potential for solubilizing insoluble phosphate, producing IAA, and fixing atmospheric nitrogen. However, only one of the selected fungal isolates was shown to be a potassium solubilizer. The antagonistic test showed that P. aeruginosa was inhibitory against T. oumae-annae. The oil palm fiber (OPF) biochars in this study were produced by two different methods: under a continuous flow of compressed air and in the presence of nitrogen gas. The OPF biochars were then mixed with 10 ppm ammoniacal nitrogen (NH3-N) for an adsorption test, and the products were labeled as air-spent OPF biochar and N2-spent OPF biochar, respectively. When B. pumilus was inoculated to these biochars, the CFU number for N2-spent OPF biochar increased threefold. However, there was no CFU recovered from the air-spent OPF biochar. In scanning electron microscopy (SEM) analysis, the cells of B. pumilus were observed to be localized on both the surface and interior of the biochar particles. These results conclude that the microbial isolates from the palm oil sludge samples are potential plant growth-promoting microbes, and the N2-spent OPF biochar was demonstrated to be a good carrier material in housing and supporting the growth of the test bacteria.