Biochemical characterization of chitinolytic Bacillus isolates from a hypersaline wetland and their biopriming potential for improving wheat germination under salinity stress.

backgroundSalinity negatively affects seed germination and crop yields. This study explored chitinolytic bacteria from the Lipar Pink Wetland as potential wheat seed-priming agents under salt stress. Using shrimp shell waste, chitinase-producing bacteria were isolated, and their live cells and chitinase-active supernatants produced on colloidal chitin were tested as wheat seed-priming treatments in normal and saline conditions.

resultsChitin extraction from shrimp shells using a conventional acid-alkali process yielded 53.3-56.7% chitin on a dry-weight basis. FTIR analysis confirmed characteristic functional groups, and FESEM revealed a compact, flake-like morphology. Among 45 bacterial isolates screened on chitin-containing media, three strains (S1, S49, and S80) formed clear hydrolysis halos and were selected for further analysis. Their chitinase-active extracellular fractions showed broad activity across 35-50 °C, with optimum temperatures of 40 °C for Sup49 and 45 °C for Sup1 and Sup80. Sup1 exhibited the highest activity under acidic conditions, whereas Sup49 and Sup80 performed best at near-neutral to slightly alkaline pH. Sup80 also showed superior thermostability at 60 °C and greater tolerance to salinity and EDTA than the other fractions. Partial 16 S rRNA phylogeny placed S49 and S80 within Bacillus cereus sensu lato-related lineages. Seed priming showed that 150 mM sodium chloride reduced wheat performance, decreasing germination in the untreated control from 73.74 ± 7.82% under normal conditions to 34.44 ± 1.92% under salinity. Under normal conditions, shorter priming durations were generally more effective. Hydropriming for 3 and 7 h produced high germination rates, while N-S80.3 h produced the numerically greatest total seedling length. Under salinity, S-Sup1.3 h showed the strongest numerical overall response, increasing germination to 74.67 ± 4.62% and producing the highest shoot length, root length, total seedling length, and seedling vigor index among saline treatments with available growth data. However, its GP was statistically grouped with S-Hydropriming.24 h and S-Sup49.7 h.

conclusionsChitinolytic Bacillus-related isolates and their chitinase-active extracellular supernatants showed preliminary potential for wheat seed priming under salinity. Because the supernatants were not purified chitinase preparations, their effects may reflect combined extracellular metabolites and chitin-derived products. Future research should focus on microbial traits, plant stress physiology, pathogen challenges, biosafety, and field performance.