Utilization of Banana Peel as a Novel Substrate for Biosurfactant Production by Halobacteriaceae archaeon AS65

In this study, biosurfactant-producing bacteria was evaluated for biosurfactant production by using banana peel as a sole carbon source. From the 71 strains screened, Halobacteriaceae archaeon AS65 produced the highest biosurfactant activity. The highest biosurfactant production (5.30 g/l) was obtained when the cells were grown on a minimal salt medium containing 35 % (w/v) banana peel and 1 g/l commercial monosodium glutamate at 30 °C and 200 rpm after 54 h of cultivation. The biosurfactant obtained by extraction with ethyl acetate showed high surface tension reduction (25.5 mN/m), a small critical micelle concentration value (10 mg/l), thermal and pH stability with respect to surface tension reduction and emulsification activity, and a high level of salt tolerance. The biosurfactant obtained was confirmed as a lipopeptide by using a biochemical test FT-IR, NMR, and mass spectrometry. The crude biosurfactant showed a broad spectrum of antimicrobial activity and had the ability to emulsify oil, enhance PAHs solubility, and oil bioremediation.     

Application of Biosurfactant from Sphingobacterium spiritivorum AS43 in the Biodegradation of Used Lubricating Oil

This study aimed at investigating the application of biosurfactant from Sphingobacterium spiritivorum AS43 using molasses as a substrate and fertilizer to enhance the biodegradation of used lubricating oil (ULO). The cell surface hydrophobicity of bacteria, the emulsification activity, and the biodegradation efficiency of ULO were measured. The bacterial adhesion in the hydrocarbon test was used to denote the cell surface hydrophobicity of the used bacterial species. The results indicate a strong correlation between cell surface hydrophobicity, emulsification activity, and the degree of ULO biodegradation. The maximum degradation of ULO (62 %) was observed when either 1.5 % (w/v) of biosurfactant or fertilizer was added. The results also revealed that biosurfactants alone are capable of promoting biodegradation to a large extent without added fertilizer. The data indicate the potential for biosurfactant production by using low-cost substrate for application in the bioremediation of soils contaminated with petroleum hydrocarbons or oils.     

Characterization and Phylogenetic Analysis of Microbial Surface Active Compound-Producing Bacteria

Microbial surface active compounds (SACs) were isolated from various environmental sources in Thailand. Isolates were screened for SACs production in different carbon sources (crude glycerol, commercial sugar, decanter, glucose, molasses, used palm oil, and used lubricating oil) by using drop-collapsing test and emulsification activity. Molasses produced the highest number of positive results (23 of 25 isolates). Twenty-one isolate strains produced emulsions with xylene, and 15 exhibited high emulsion-stabilizing capacity, maintaining more than 50?% of the original emulsion volume for 24?h, and six isolate strains reduced the growth medium surface tension to 40?mN/m. The phylogenetic position of these 25 isolates was evaluated by 16S rRNA gene sequence analysis. The production of microbial SACs was determined for strains representative of 16 different bacterial genera, in which ten genera (Blastococcus, Erysipelothrix, Humicoccus, Methylophilus, Microlunatus, Nevskia, Pectinatus, Rubrimonas, Selenomonas, and Stenotrophomonas) were firstly reported as SAC-producing strains. Overall, the new SAC-producing strains isolated in this study display promising features for the future development and use in economically efficient industrial-scale biotechnological processes.     

Molasses as a whole medium for biosurfactants production by Bacillus strains and their application

Two types of biosurfactant (BS)-producing bacteria, Bacillus licheniformis TR7 and Bacillus subtilis SA9, were isolated from mangrove sediment in the south of Thailand. The BS production was done by using only molasses as a whole medium for growth and production. Under optimized conditions, the yields of TR7 and SA9 BS were found to be 3.30 and 3.78 g/l, respectively. It could reduce the surface tension of pure water to 28.5 and 29.5 mN/m, with the critical micelle concentrations of about 10 and 30 mg/l, respectively. Good thermal, pH, and salt stability were exhibited. Both BSs could recover oil more effectively than the two synthetic surfactants. In addition, TR7 and SA9 BS could enhance the solubility of polyaromatic hydrocarbons (PAHs). Thus, these BSs have the potential for the removal of oil and PAHs from the combined contaminated environment and facilitate its bioremediation. These studies indicate that molasses, as a renewable, relatively inexpensive and easily available resource, can be used for important biotechnological processes.