Studies on the Effects of Bioprocess Parameters and Kinetics of Rhamnolipid Production by P. aeruginosa NITT 6L

Biosurfactants are gaining popularity in recent times due to lower toxicity, biodegradability, environmental compatibility and activity in extreme conditions. An air isolate was isolated previously for biosurfactant production in our laboratory, and characterized and named as P. aeruginosa NITT 6L. The biosurfactant thus produced was characterized to be surface-active rhamnolipid. This paper presents the study of the influence of various bioprocess parameters such as agitation, aeration and inoculum volume on rhamnolipid production by the isolate. Kinetics of rhamnolipid production in optimized media and process conditions were investigated. The rhamnolipid production was found to be increased after nitrogen depletion during stationary phase. The maximum rhamnolipid concentration of about 7.65 g L–1 was achieved after 96 h. Logistic model was found to be satisfactory in fitting the microbial growth. Emulsification activity of the crude rhamnolipid extract with different hydrocarbons was studied. The crude extract of rhamnolipid reduced the surface tension of water from 71.4 to 27.5 mN m–1, and CMC was about 11 mg L–1. Also, the usefulness of the extracted rhamnolipid produced under optimal conditions was investigated for remediation of crude oil contaminated soil. Soil washing with 0.3 % rhamnolipid removed about 71 % of crude oil present in sand samples within 24 h

Bacillus cereus KLUVAA Mediated Biocement Production Using Hard Water and Urea

In the present study, a potential bacterial strain with maximum urease activity was isolated from urea-rich paddy field soil for biocement production. The bacterial isolate was screened using Christensen selective agar media and named as KLUVAA. This isolate was found to be tolerant up to 10 % urea. 16S rRNA sequencing analysis identified the isolate KLUVAA as Bacillus cereus. Biocement production was carried out using tap water with 431.7 mg L–1 of hardness as a natural source of calcium. Functional groups present in biocement were analysed using FT-IR spectrum. The morphology and elemental composition of the biocement was studied using SEM with EDS mapping and XRD analyses. Thermogravimetric analysis was used to study the thermal stability of the microbial biocement. Further, process parameters were optimized for enhancing the yield of biocement. This work is licensed under a Creative Commons Attribution 4.0 International License

Dual substrate fermentation using palm oil and glucose for production of eco-friendly biosurfactants using <em>P. aeruginosa</em> NITT 6L

101-105Studies have been conducted to improve biosurfactant (rhamnolipid) production from Pseudomonas aeruginosa NITT 6L in liquid state fermentation utilizing palm oil and glucose as substrates. The pH and minimal salt media (MSM) compositions such as KH2PO4, K2HPO4, NaNO3, MgSO4, NaCl and FeSO4 are optimized using design of experiments. One-factor-at-a-time optimization is employed to evaluate the effects of palm oil and its co-substrate glucose on biosurfactant production. The optimal levels of the aforementioned variables are (g/L) glucose 30.0, KH2PO4 2.0, K2HPO4 5.0, NaNO3 3.5, FeSO4 0.003, MgSO4 0.2, with palm oil concentration of 1.5% (v/v). The fermentation conditions viz. period of fermentation, agitation rate, aeration and concentration of inoculum are optimized by carrying out separate experimentations. The optimum period of fermentation, agitation rate, aeration and concentration of inoculum in the fermentation medium  are found to be 7 days, 150 rpm, 60% and 2% (v/v), respectively, for  maximum rhamnolipid production of about 3.73 g/RE l