Description of novel marine bioflocculant-producing bacteria isolated from biofloc of Pacific whiteleg shrimp,Litopenaeus vannameiculture ponds

Abstract

19Description of marine bioflocculant-producing bacteria isolated from biofloc of 20 Pacific whiteleg shrimp, Litopenaeus vannamei culture ponds was prompted to 21 explore the bacteria that enhanced bioflocculation process in aquaculture wastewater 22 treatment. Certain marine bacteria were potentially secreted extracellular polymeric 23 substances (EPS) which response to the physiological stress encountered in the natural 24 environment that can act as bioflocculants. This study aimed to identify marine 25 2 bioflocculant-producing bacteria isolated from biofloc; to evaluate their flocculating 26 activities; and to characterize their protein in EPS. Phenotypic and genotypic 27 identification of the bacteria including morphological and molecular approaches were 28 employed, while their flocculating activities were examined via Kaolin clay 29 suspension method and statistically analyzed. The EPS that acted as bioflocculants 30 were extracted using cold ethanol precipitation method. Protein concentration was 31 determined by Bradford assay and protein profiling was finally completed with 32 Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) method. 33 Six species of marine bacteria known as Halomonas venusta, Bacillus cereus, Bacillus 34 subtilis, Bacillus pumilus, Nitratireductor aquimarinus and Pseudoalteromonas sp. 35 were successfully identified as bioflocculant-producing bacteria. The highest 36 flocculating activity was exhibited by Bacillus cereus at 93%, while Halomonas 37venusta showed the lowest record at 59%. All bioflocculant-producing bacteria 38 species showed different protein concentration that ranged between 1.377 µg/mL to 39 1.455 µg/mL. Several protein bands with different molecular weight that ranged 40 between 16 kDa to 100 kDa were observed. This study revealed that all the identified 41 bacteria species have high potential characteristics to initiate aquaculture wastewater 42 treatment and may play important roles in bioflocculation process. 43 Importance: 46 Six species of marine bacteria isolated from biofloc of Pacific whiteleg shrimp, 47 Litopenaeus vannamei culture ponds were identified as bioflocculant-producing 48 bacteria. Among those six species, Bacillus cereus, Bacillus pumilus, Nitratireductor 49 3 aquimarinus and Pseudoalteromonas sp. were highly potential to be used as booster 50 for rapid formation of biofloc due to their high flocculating activities. Protein content 51 in EPS of novel marine biofocculant-producing bacteria has beneficial consequences 52 on degradation process of organic substances, denitrification of wastes and ions 53 elimination from aquaculture wastes.54

Isolation, characterization and performance of extra cellular polymer substances (EPS) producing bacteria from biofloc culture water of Nile tilapia using distillery spentwash as carbon source

“…The identified isolates were dominantly Bacillus sp. which agrees with the findings of Hashim et al (2018). Previous studies have also reported on the presence of bioflocculating bacteria in biofloc culture ponds of P. vannamei (Kasan et al 2016).…”