Comparative study of various carbon sources on rhamnolipid production

Ehinmitola, Emmanuel Olufemi; Aransiola, Elizabeth Funmilayo; Adeagbo, Oluwaseyi Peter

doi:10.1016/j.sajce.2018.09.001

“…Though all the tested substrates can be used as carbon sources for production of rhamnolipids by P. aeruginosa under aerobic conditions [21][22][23][24]. In this study, only glycerol can be used for anaerobic production of rhamnolipids by P. aeruginosa strains among the tested substrates.…”

Section: Resultsmentioning

confidence: 92%

Glycerol promoted the anaerobic production of rhamnolipids by different Pseudomonas aeruginosa strains

Zhao

¹

,

Zheng

²

,

Cui

³

2021

Preprint

0

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Background: Rhamnolipids is the most widely studied and applied biosurfactants. The anaerobic biosynthesis of rhamnolipids has important research and practical significance, such as meeting the in situ production of biosurfactant in anoxic environments and the foamless fermentation of biosurfactants. A few studies have reported the anaerobic biosynthesis of rhamnolipids from rare Pseudomonas aeruginosa strains. What did promote the anaerobic biosynthesis of rhamnolipids, the specificity of the rare strains or the effect of specific substrates? Here, anaerobic production of rhamnolipids by different P. aeruginosa strains was investigated using diverse substrates. The anaerobic biosynthesis mechanism of rhamnolipids were also discussed from the substrate point of view.Results: All P. aeruginosa strains anaerobically grew well using the tested substrates. But all P. aeruginosa strains anaerobically produced rhamnolipids only using substrates containing glycerol and nitrate. Fourier transform infrared (FTIR) spectra analysis confirmed the anaerobic production of rhamnolipids from all P. aeruginosa strains. All the anaerobically produced rhamnolipids decreased air-water surface tension from 72.6 mN/m to below 29.0 mN/m and emulsified crude oil with EI24 above 65%. Using crude glycerol as low-cost substrate, all P. aeruginosa strains can anaerobically grow and produce rhamnolipids to reduce the culture surface tension below 35 mN/m. The glycerol metabolic intermediate, 1, 2-propylene glycol, can also achieve the anaerobic production of rhamnolipids by all P. aeruginosa strains.Conclusions: Not the specificity of the rare P. aeruginosa strains but the effect of specific substrates promote the anaerobic biosynthesis of rhamnolipids by P. aeruginosa. Glycerol and nitrate are the excellent substrates for anaerobic production of rhamnolipids from all P. aeruginosa strains. Results indicated that glycerol metabolism involveed the anaerobic biosynthesis of rhamnolipids in P. aeruginosa. Results also showed the feasibility of using crude glycerol as low cost substrate to anaerobically biosynthesize rhamnolipids by P. aeruginosa.

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“…Though all the tested substrates can be used as carbon sources for production of rhamnolipids by P. aeruginosa under aerobic conditions [22][23][24][25]. In this study, only glycerol can be used for anaerobic production of rhamnolipids by P. aeruginosa strains among the tested substrates.…”

Section: Resultsmentioning

confidence: 92%

Glycerol promoted the anaerobic production of rhamnolipids by different Pseudomonas aeruginosa strains

Zhao

¹

,

Guo

²

,

Cui

³

2020

Preprint

0

View full text Add to dashboard Cite

Background: Rhamnolipids is the most widely studied and applied biosurfactants. The anaerobic biosynthesis of rhamnolipids has important research and practical significance, such as meeting the in situ production of biosurfactant in anoxic environments and the foamless fermentation of biosurfactants. A few studies have reported the anaerobic biosynthesis of rhamnolipids from rare Pseudomonas aeruginosa strains. What did promote the anaerobic biosynthesis of rhamnolipids, the specificity of the rare strains or the effect of specific substrates? Here, anaerobic production of rhamnolipids by different P. aeruginosa strains was investigated using diverse substrates. The anaerobic biosynthesis mechanism of rhamnolipids were also discussed from the substrate point of view.Results: All P. aeruginosa strains anaerobically grew well using the tested substrates. But all P. aeruginosa strains anaerobically produced rhamnolipids only using substrates containing glycerol and nitrate. Fourier transform infrared (FTIR) spectra analysis confirmed the anaerobic production of rhamnolipids from all P. aeruginosa strains. All the anaerobically produced rhamnolipids decreased air-water surface tension from 72.6 mN/m to below 29.0 mN/m and emulsified crude oil with EI24 above 65%. Using crude glycerol as low-cost substrate, all P. aeruginosa strains can anaerobically grow and produce rhamnolipids to reduce the culture surface tension below 35 mN/m. The glycerol metabolic intermediate, 1, 2-propylene glycol, can also achieve the anaerobic production of rhamnolipids by all P. aeruginosa strains.Conclusions: Not the specificity of the rare P. aeruginosa strains but the effect of specific substrates promote the anaerobic biosynthesis of rhamnolipids by P. aeruginosa. Glycerol and nitrate are the excellent substrates for anaerobic production of rhamnolipids from all P. aeruginosa strains. Results indicated that glycerol metabolism involveed the anaerobic biosynthesis of rhamnolipids in P. aeruginosa. Results also showed the feasibility of using crude glycerol as low cost substrate to anaerobically biosynthesize rhamnolipids by P. aeruginosa.

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“…Previous studies using Bushnell-Haas medium supplemented with 1% Glucose, Varjani and Vivek have reported biosurfactant yield of about 3.178± 0.071g/l at 96 h. 30 Moreover, various studies have recorded the use of glucose as carbon source in the production of biosurfactant from Pseudomonas aeruginosa and has reported a yield of 1.0-1.6g/l. [31][32][33] Also, LB broth was assessed for biosurfactant concentration and the yield harvested by LB broth (Supplementary Figure 1a) at 48h (11.07±0.15 mg/ml) was higher than that of Bushnell Haas medium supplemented with 1% Glucose (Figure 1b). Although using economical carbon sources Mukherjee et al have reported biosurfactant yield of 45g/l.…”

Section: Discussionmentioning

confidence: 99%

“…4 The biosurfactant produced from Pseudomonas aeruginosa using Luria-Broth demonstrated high emulsification activity with kerosene (70%). 33,36 Also, Al Wahaibi et al has reported 50% of crude oil emulsification with less biosurfactant production (0.5g/ml) by Bacillus subtilis B30. 37 Similarly, Dastgheib et al have reported 65% of crude oil emulsification by Bacillus strains.…”

Section: Discussionmentioning

confidence: 99%