THE ABILITY OF PGPR ISOLATES FROM IRON SAND SOIL TO PRODUCE EXOPOLYSACCHARIDES IN ATCC NO. 14 MEDIUM WITH DIFFERENT CARBON SOURCES

Abstract

Coastal land is marginal with low soil fertility and agricultural productivity. Plant growth-promoting rhizobacteria (PGPR) that produce exopolysaccharides (EPS) can increase plant resistance and soil aggregate stability. This study aimed to determine the ability of PGPR isolates from iron sand soil to produce EPS in American Type Culture Collection (ATCC) No. 14 medium, identify the optimal carbon source, and determine the highest EPS production time for selected isolates. The effect of carbon sources on EPS production by selected isolates was studied using a Completely Randomized Design (CRD). The treatments consisted of six different carbon sources (control, glucose, fructose, sucrose, lactose, and mannitol), and each treatment was replicated three times. The data were analyzed using ANOVA and followed by the Honestly Significant Difference (HSD) test. The results showed that 16 PGPR isolates had the potential to produce EPS, with isolate PT4C5 exhibiting the highest slime index. The crude EPS production test showed that sucrose was the optimal carbon source, at 12.89 mg/L. The EPS production of isolate PT4C5 in ATCC No. 14 medium with sucrose peaked at 36 hours of incubation at 23.11 mg/L. The results also indicated that isolate type, carbon source, and fermentation time are important factors for optimizing EPS production by PGPR isolates.