Accurate investigation of the mechanism of rhamnolipid biosurfactant effects on food waste composting: A comparison of in-situ and ex-situ techniques.

The long process time and low product quality are major challenges in the composting process. To overcome the above challenges, the effects of produced biosurfactants on composting were investigated as a biological model. Pseudomonas aeruginosa IBRC-M 11180 inoculum and its supernatant were used as in-situ and ex-situ treatments in the composting process, respectively. The results showed that the presence of rhamnolipid biosurfactants in the composting process could improve many parameters such as maximum temperature, electrical conductivity (EC), cation exchange capacity (CEC), C/N, and germination index (GI). The GI value above 80% was observed for in-situ and ex-situ reactors on 12th day, while for the control was observed on 18th day, which indicates the significant effects of rhamnolipids on process time reduction. The C/N ratios of final compost for ex-situ, in-situ, and control reactors were 12.83, 13.27, and 17.05, respectively, which indicates the rhamnolipids also improves the quality of the final product. To better understand the performance of the rhamnolipids in the composting, wettability changes of the compost surface were evaluated. Our results show that the produced rhamnolipids altered the waste wettability from intermediate wet (θ = 85°) to water-wet (θ = 40°). It can be concluded that the presence of biosurfactants in composting leads to an increase in the contact surface area of microorganisms with nutrient sources and consequently improves the composting process. Furthermore, comparative studies showed that the in-situ treatment has better effects on composting, thus it can be an economically significant achievement because of the high cost of ex-situ treatment.

Improving municipal solid waste compost process by cycle time reduction through inoculation of Aspergillus niger.

A lack of understanding about the effect of microorganism inoculation on compost production and relatively expensive downstream processing are the main obstacles towards an economic compost production. Our work tries to fill this gap. For this, influence of inoculation on the composting of organic fraction of municipal solid waste (OFMSW) to produce compost with higher agronomic value was evaluated. Three similar aerated bioreactors (A, B and C) with the same size and shape in laboratory scale designed. Reactor A was inoculated with the Aspergillus niger IBRC-M 30095, reactor B was inoculated with old compost and reactor C was used as a control. During the composting process temperature, moisture, pH, and electrical conductivity (EC) were evaluated. Also, the ratio of carbon to nitrogen (C/N) and germination index (GI) were measured in during process to evaluate compost maturity. The results of this study showed that the C/Ns decreased to about 63.37%, 59.6% and 46% for bioreactors B, A and control, respectively. Also maximum GI and temperature reached to about 138% and 59 °C in reactor B. Furthermore, our results showed that inoculation with this microorganism reduces process time to 18 days that is better than the results of other researchers and thus results in cost savings. However, we think, Aspergillus niger is appropriate candidate for compost production as a model. Graphical abstractSchematic diagram of experimental reactors: Reactor A was inoculated with the Aspergillus Niger IBRC-M 30095, reactor B was inoculated with old compost and reactor C used as a control without inoculation; (1) composting tank; (2) air compressor; (3) gas flow meter; (4) air regulator; (5) thermal probe; (6) exhausted gas; (7) mixer; (8) effluent; (9) moisture content probe; (10) sampling; (11) electric motor; (12) pump.

Introduction of 5-aminolevulinic acid as a theranostics agent in dentistry.

OBJECTIVE: The aim of this paper is to study the theranostic potential of 5-Aminolevulinic Acid (5-ALA)in dentistry. METHODS: Photodynamic inactivation (PDI) and fluorescence spectroscopy of Streptococcus sanguis, and laser induced fluorescence (LIF) of several decayed teeth were performed using 5-ALA. RESULTS: In the absence of 5-ALA, 15 min illumination of the bacteria by the means of an LED light source led to only 1.16% viability reduction. On the other hand, 5-ALA revealed remarkable dark toxicity at concentrations above 20 µM. Furthermore, the synergistic effects of 10 µM 5-ALA and illumination by the light source for 5 and 15 min intervals led respectivelyto0.74log10 and 1.69log10 reduction of viability. Also, fluorescence spectroscopy of the bacteria showed a direct relationship between emission line intensity at 620 nm and the concentration of 5-ALA. In dental experiments, following exposing tooth with 40 mM 5-ALA, a significant autofluorescence growth was observed just in the decayed parts. CONCLUSION: Based on the strong dual modality of 5-ALA to annihilate cariogenic bacteria through photodynamic inactivation and enhancing LIF intensity for identification of dental caries, 5-ALA is proposed as a theranostic agent in dentistry.

Rhamnolipid as new bio-agent for cleaning of ultrafiltration membrane fouled by whey.

In this work, rhamnolipid biosurfactant as an eco-friendly and biodegradable cleaning agent was produced by Pseudomonas aeruginosa bacteria and was used to evaluate the chemical cleaning efficiency of whey fouled ultrafiltration membranes. Thin layer chromatography (TLC) and Fourier transform infrared spectroscopy (FTIR) confirmed the successful synthesis of rhamnolipid. The produced rhamnolipid was compared to chemical cleaners including sodium hydroxide (NaOH), sodium dodecyl sulfate (SDS) and Tween 20. Ultrafiltration membranes used for fouling and cleaning analysis were prepared using phase inversion via immersion precipitation technique. For studying the fouling mechanisms, Hermia's model adapted to cross-flow was used. From the fouling mechanism experiments, it was found that the complete blocking and cake formation were the dominant fouling mechanisms. The highest values of cleaning efficiency were achieved using rhamnolipid and NaOH as cleaning agents with the flux recovery of 100%, but with considering the low concentration of the rhamnolipid used in the cleaning solution compared to NaOH (0.3 versus 4 g/L for NaOH), its application is preferred.

Photodynamic Inactivation of E. coli PTCC 1276 Using Light Emitting Diodes: Application of Rose Bengal and Methylene Blue as Two Simple Models.

The lack of a comparative study about potential of high-power light emitting diodes (LEDs) for photodynamic inactivation (PDI) of pathogenic microorganisms has remained as a challenging issue for researchers. Therefore, the aim of this study is to fill this gap through introduction of an efficient model for in vitro PDI in an aqueous medium. For this purpose, two individual 30 mW/cm2 irradiation systems were designed using suitable sets of green and red LEDs. At another work, Methylene blue (MB) and Rose bengal (RB) as two simple models in the range of 5-150 µM were used in order to compare PDI of E. coli PTCC 1276 using red and green LED systems. Our results showed that a first-order mathematical model has the strength to describe the temporal variation of survival curves. Based on our results, when concentration of photosensitizer increased, the rate of inactivation for RB increased while MB depicted a maximum rate value at 25 µM. In a comparative study, optimum inactivation of E. coli PTCC 1276 obtained during 2- and 10-min irradiation of the LED systems using RB and MB at 150 and 25 µM, respectively. With regard to lower value of inactivation time and higher rate of inactivation for RB, use of simultaneous green high-power LEDs and RB is proposed as an efficient approach for PDI of pathogenic bacteria in future industrial applications.

Production of microbial rhamnolipid by Pseudomonas aeruginosa MM1011 for ex situ enhanced oil recovery.

Recently, several investigations have been carried out on the in situ bacteria flooding, but the ex situ biosurfactant production and addition to the sand pack as agents for microbial enhanced oil recovery (MEOR) has little been studied. In order to develop suitable technology for ex situ MEOR processes, it is essential to carry out tests about it. Therefore, this work tries to fill the gap. The intention of this study was to investigate whether the rhamnolipid mix could be produced in high enough quantities for enhanced oil recovery in the laboratory scale and prove its potential use as an effective material for field application. In this work, the ability of Pseudomonas aeruginosa MM1011 to grow and produce rhamnolipid on sunflower as sole carbon source under nitrogen limitation was shown. The production of Rha-C10-C10 and Rha2-C10-C10 was confirmed by thin-layer chromatography and high-performance liquid chromatography analysis. The rhamnolipid mixture obtained was able to reduce the surface and interfacial tension of water to 26 and 2 mN/m, respectively. The critical micelle concentration was 120 mg/L. Maximum rhamnolipid production reached to about 0.7 g/L in a shake flask. The yield of rhamnolipid per biomass (Y RL/x ), rhamnolipid per sunflower oil (Y RL/s ), and the biomass per sunflower oil (Y x/s ) for shake flask were obtained about 0.01, 0.0035, and 0.035 g g(-1), respectively. The stability of the rhamnolipid at different salinities, pH and temperature, and also, its emulsifying activity has been investigated. It is an effective surfactant at very low concentrations over a wide range of temperatures, pHs, and salt concentrations, and it also has the ability to emulsify oil, which is essential for enhanced oil recovery. With 120 mg/L rhamnolipid, 27 % of original oil in place was recovered after water flooding from a sand pack. This result not only suggests rhamnolipids as appropriate model biosurfactants for MEOR, but it even shows the potential as a biosurfactant of choice for actual MEOR applications.

Scale up and application of biosurfactant from Bacillus subtilis in Enhanced Oil recovery.

There is a lack of fundamental knowledge about the scale up of biosurfactant production. In order to develop suitable technology of commercialization, carrying out tests in shake flasks and bioreactors was essential. A reactor with integrated foam collector was designed for biosurfactant production using Bacillus subtilis isolated from agricultural soil. The yield of biosurfactant on biomass (Y(p/x)), biosurfactant on sucrose (Y(p/s)), and the volumetric production rate (Y) for shake flask were obtained about 0.45 g g(-1), 0.18 g g(-1), and 0.03 g l(-1) h(-1), respectively. The best condition for bioreactor was 300 rpm and 1.5 vvm, giving Y(x/s), Y(p/x), Y(p/s), and Y of 0.42 g g(-1), 0.595 g g(-1), 0.25 g g(-1), and 0.057 g l(-1) h(-1), respectively. The biosurfactant maximum production, 2.5 g l(-1), was reached in 44 h of growth, which was 28% better than the shake flask. The obtained volumetric oxygen transfer coefficient (K(L)a) values at optimum conditions in the shake flask and the bioreactor were found to be around 0.01 and 0.0117 s(-1), respectively. Comparison of K(L)a values at optimum conditions shows that biosurfactant production scaling up from shake flask to bioreactor can be done with K(L) a as scale up criterion very accurately. Nearly 8% of original oil in place was recovered using this biosurfactant after water flooding in the sand pack.