Characterization of Enterobacter cloacae BAGM01 Producing a Thermostable and Alkaline-Tolerant Rhamnolipid Biosurfactant from the Gulf of Mexico

Abstract

The search for novel biosurfactants (Bs) requires the isolation of microorganisms from different environments. The Gulf of Mexico (GoM) is a geographical area active in the exploration and exploitation of hydrocarbons. Recent metagenomic and microbiologic studies in this area suggested a potential richness for novel Bs microbial producers. In this work, nineteen bacterial consortia from the GoM were isolated at different depths of the water column and marine sediments. Bs production from four bacterial consortia was detected by the CTAB test and their capacity to reduce surface tension (ST), emulsion index (EI 24 ), and hemolytic activity. These bacterial consortia produced Bs in media supplemented with kerosene, diesel, or sucrose. Cultivable bacteria from these consortia were isolated and identified by bacterial polyphasic characterization. In some consortia, Enterobacter cloacae was the predominant specie. E. cloacae BAGM01 presented Bs activity in minimal medium and was selected to improve its Bs production using a Taguchi and Box-Behnken experimental design; this strain was able to grow and presented Bs activity at 35 g L −1 of NaCl. This Bs decreased ST to around 34.5 ± 0.56 mNm −1 and presented an EI 24 of 71 ± 1.27%. Other properties of this Bs were thermal stability, stability in alkaline conditions, and stability at high salinity, conferring important and desirable characteristics in multiple industries. The analysis of the genome of E. cloacae BAGM01 showed the presence of rhlAB genes that have been reported in the synthesis of rhamnolipids, and alkAB genes that are related to the degradation of alkanes. The bioactive molecule was identified as a rhamnolipid after HPLC derivatization, 1 H NMR, and UPLC-QTOF-MS analysis.

Exploration and characterization of a newly isolated bacterium, Enterobacter quasihormaechei strain BDIFST24001, capable of producing rhamnolipid biosurfactant for oil remediation

“…Additionally, Rooney et al [ 12 ] reported the production of rhamnolipid biosurfactant from E. hormaechei , achieving a similar surface tension reduction to our findings. Emulsification activities of E. hormaechei on various hydrocarbons and edible oils were observed in our experiment, corroborated by studies by Curiel-Maciel et al [ 30 ]. It is crucial to note that while some Enterobacter species could be pathogenic to humans, not all strains within these species possess virulence factors necessary to cause infection.…”

“…The emulsification index (EI24) of the study isolates ranged from 13.33±0.02% (B18) to 66.29±0.03% (B24). Similarly, Curiel-Maciel et al [ 30 ] observed an emulsification index range of 19.6–63.2% in their study [ 30 ]. The highest emulsification activity was demonstrated by isolate B24 (66.3 %) on kerosene oil, followed by B22 (EI24 63.33 %), B12 (EI24 55.56%) and B20 (EI24 53.33%).…”

“…Values of the emulsification index exceeding 40% are generally considered satisfactory [ 31 ]. Previous research indicates that the emulsification index value for kerosene oil typically ranges from 42% to 55% [ 30 ]. It is important to note that the stable interaction between the hydrophobic and hydrophilic phases, resulting in emulsion formation, is largely influenced by the solvents used [ 22 32 ].…”

Definition of the Metagenomic Profile of Ocean Water Samples From the Gulf of Mexico Based on Comparison With Reference Samples From Sites Worldwide

“…Notably, the results related to the presence of enzymes involved in oil degradation are consistent with previous works of our own and other groups that investigated the Mexican exclusive economic zone and identified oil-degrading microorganisms derived from 16S amplicon analysis (Fernanda Sánchez-Soto Jiménez et al, 2018;Godoy-Lozano et al, 2018;Hernández-López et al, 2019;Moreno-Ulloa et al, 2019;Raggi et al, 2020;Ramírez et al, 2020); isolated fractions related to petroleum (Moreno-Ulloa et al, 2019); isolated consortia and species capable of degrading petroleum under aerobic and anaerobic conditions (Muriel-Millán et al, 2019;Curiel-Maciel et al, 2021;Rosas-Díaz et al, 2021); and characterized petroleum-degrading enzymes (Rodríguez-Salazar et al, 2020), even in regions with no evidence of anthropogenic perturbation. A recent review illustrated the distribution of bacteria in the water column and sediments of the Mexican exclusive economic zone of the GoM (Rodríguez-Salazar et al, 2021).…”

Multifunctional, stable and low-cost lipopeptide biosurfactant produced by Enterobacter cloacae UCP 1597

“…On the other hand, the thermostability of the biosurfactant at 10-100ºC (Figure 6B) was evidenced, in agreement with the studies performed by Jamil et al ( 2018) and Curiel-Maciel et al (2021). At 5°C, there was an increase in surface tension (~40 mN/m), suggesting that this surfactant has a Krafft temperature (also known as critical micellar temperature) (Perfumo, et al, 2018) at low values, similar to the biosurfactant lipopeptide produced by Bacillus subtilis N3-1P (Zhu, et al, 2020).…”