This study was aimed at the development of economical methods for higher yields of biosurfactant by suggesting the use of low‐cost raw materials. Two oil‐degrading strains, Pseudomonas aeruginosa GS9–119 and DS10–129, were used to optimize a substrate for maximum rhamnolipid production. Among the two strains, the latter produced maxima of 4.31, 2.98, and 1.77 g/L rhamnolipid biosurfactant using soybean oil, safflower oil, and glycerol, respectively. The yield of biosurfactant steadily increased even after the bacterial cultures reached the stationary phase of growth. Characterization of rhamnolipids using mass spectrometry revealed the presence of dirhamnolipids (Rha‐Rha‐C 10 –C 10 ). Emulsification activity of the rhamnolipid biosurfactant produced by P. aeruginosa DS10–129 was greater than 70% using all the hydrocarbons tested, including xylene, benzene, hexane, crude oil, kerosene, gasoline, and diesel. P. aeruginosa GS9–119 emulsified only hexane and kerosene to that level.
6 April 2017 in Applied Microbiology and Biotechnology
High production cost and potential pathogenicity of Pseudomonas aeruginosa, commonly used for rhamnolipid synthesis, have led to extensive research for safer producing strains and cost-effective production methods. This has resulted in numerous research publications claiming new non-pathogenic producing strains and novel production techniques many of which are unfortunately without proper characterisation of product and/or producing strain/s. Genes responsible for rhamnolipid production have only been confirmed in P. aeruginosa, Burkholderia thailandensis and Burkholderia pseudomallei. Comparing yields in different publications is also generally unreliable especially when different methodologies were used for rhamnolipid quantification. After reviewing the literature in this area, we strongly feel that numerous research outputs have insufficient evidence to support claims of rhamnolipid-producing strains and/or yields. We therefore recommend that standards should be set for reporting new rhamnolipid-producing strains and production yields. These should include (1) molecular and bioinformatic tools to fully characterise new microbial isolates and confirm the presence of the rhamnolipid rhl genes for all bacterial strains, (2) using gravimetric methods to quantify crude yields and (3) use of a calibrated method (high-performance liquid chromatography or ultra-performance liquid chromatography) for absolute quantitative yield determination.
Although biofilms are recognised as important in microbial colonisation, solutions to their inhibition are predominantly based on planktonic assays. These solutions have limited efficacy against biofilms. Here, a series of biofilm-orientated tests were used to identify anti-biofilm compounds from marine micro-flora. This led to the isolation of a complex of anti-biofilm compounds from an extract of Paenibacillus polymyxa (PPE). A combination of rpHPLC and mass spectrometry identified the principle components of PPE as fusaricidin B (LI-FO4b) and polymyxin D1, with minor contributions from surfactins. This complex (PPE) reduced the biofilm biomass of Bacillus subtilis, Micrococcus luteus, Pseudomonas aeruginosa, Staphylococcus aureus and Streptococcus bovis. In contrast, ampicillin was only effective against S. aureus. PPE also inhibited a self-assembling marine biofilm (SAMB) in co-incubation assays by 99.3% ± 1.9 and disrupted established SAMB by 72.4% ± 4.4, while ampicillin showed no significant reduction. The effectiveness of this complex of lipopeptides against single and multispecies biofilms suggests a future role in biofilm prevention strategies.
Active and collaborative learning provides distinct advantages for students in higher education, yet can often be hampered by the barrier of large class sizes. Solutions that combine a ‘bring your own device culture’ with cloud-based technologies may facilitate a more interactive learning experience. In this pilot study, we describe the use of one such technology, Nearpod, to enhance interactivity in lectures delivered to pharmacy and bioscience students at Ulster University. Existing material in PowerPoint or Keynote format is uploaded to the instructor area of Nearpod, interactive elements are added, and the lecture is then broadcasted via the internet to student devices. The lecturer may choose to share polling responses or examples of submissions from the drawing tool or open-ended questions, thereby providing instant feedback on learning. Students commented favourably on the interactivity and engagement afforded by Nearpod. Most students were happy to use their own electronic devices (smartphones, tablets and laptops) for such activities with a minority expressing concern over problems with connecting to the institutional Wi-Fi. Nearpod and similar products represent a new class of feature-rich audience response systems that have potential to transform learning even in large classes.