Biodesulfurization of dibenzothiophene and its alkylated derivatives through the sulfur-specific pathway by the bacterium RIPI-S81

RIPI-S81 is a new dibenzothiophene (DBT)-desulfurizing bacterium, which was isolated by Research Institute of Petroleum Industry in Iran. Resting cells and growing cells of RIPI-S81 was able to convert alkylated dibenzothiophenes (Cx DBTs) to hydroxybiphenyls such that they were almost stoichiometrically accumulated as the dead-end metabolites of Cx-DBTs desulfurization in the medium containing minimal salt (MSM) and nutrients. RIPI-S81 could desulfurize up to 80% of 4,6- dimethyldibenzothiophene and 50% of methyldibenzothiophene in the MSM containing 40 mg/l of a sulfur source. The molecular structures of metabolites and the reduction of Cx-DBTs were analyzed using GC-MS and HPLC. The position of alkyl substitutes and the sulfur substrate affected desulfurization rates.Keywords: Biodesulfurization, dibenzothiophene, 4, 6-dimethyldibenzothiophene, 4-methyldibenzothiophen

Natural Pigment Production by Monascus purpureus: Bioreactor Yield Improvement through Statistical Analysis

Among the ways of pigment production, microbial synthesis has gained more interest for high growth rate, easy extraction and high yield. Pigments are used in the food industry as natural colorants and preservatives; they also have pharmaceutical applications. In this study, fungus Monascus purpureus PTCC 5303 was used to produce red, orange and yellow pigments. At first, significant variables were screened based on Plackett-Burman’s design. The optimized value of two effective factors, i.e. concentration of yeast extract and K2HPO4 by three-level, was more studied by the response surface method (RSM). The most suitable level was 2.75 g/L for yeast extract and 1.5 g/L for K2HPO4. Antimicrobial activity of the pigments was shown on Gram-positive food-borne bacteria under optimal conditions. Moreover, pigment production at optimal conditions in a bioreactor was evaluated, and the rate of production of red, orange and yellow pigments was obtained to be 2.05, 1.55 and 0.78 (ODU/ml), respectively. 

Optimization of Monacolin Production in a Controlled System

Monascus purpureus is a fungus that had been cultured on the rice in eastern Asian countries since thousands years ago and used as a food for long years. The fungus produces very valuable metabolites with polyketide structure. The most important metabolite is Monacolin K, lovastatin or competitive inhibitor of 3-Hydroxy-3-Methylglutaryl-Coenzyme A reductase (an affective enzyme in cholesterol synthesis). This metabolite has various properties including reducing blood cholesterol, preventing infection, and treatment of progressive renal disease, a variety of tumors, vascular diseases and bone fractures. In this study, Monascus purpureus PTCC5303 has been used for lovastatin production in liquid fermentation. The nutritional concentrations that were significant in biomass and lovastatin production including maltose and MgSO4 were optimized by Response Surface Methodology in a mili-bioreactor. The optimum concentration of maltose and MgSO4 was obtained as 10 g l-1 and 0.78 g l-1, respectively. According to our results, maximum lovastatin production under optimum conditions including maltose 10 g l-1, peptone 5 g l-1, MgSO4.7H2O 0.78 g l-1, MnSO4.H2O 0.5 gl-1, KH2PO4 4 g l-1, thiamine 0.1 g l-1, and pH=7 at 30 °C, 130 rpm and flow rate 1.8 l min-1 was obtained to be 309 μg l-1 after 10 days of fermentation period

Biodesulfurization of dibenzothiophene and its alkylated derivatives through the sulfur-specific pathway by the bacterium RIPI-S81

RIPI-S81 is a new dibenzothiophene (DBT)-desulfurizing bacterium, which was isolated by Research Institute of Petroleum Industry in Iran. Resting cells and growing cells of RIPI-S81 was able to convert alkylated dibenzothiophenes (Cx-DBTs) to hydroxybiphenyls such that they were almost stoichiometrically accumulated as the dead-end metabolites of Cx-DBTs desulfurization in the medium containing minimal salt (MSM) and nutrients. RIPI-S81 could desulfurize up to 80% of 4,6-dimethyldibenzothiophene and 50% of methyldibenzothiophene in the MSM containing 40 mg/l of a sulfur source. The molecular structures of metabolites and the reduction of Cx-DBTs were analyzed using GC-MS and HPLC. The position of alkyl substitutes and the sulfur substrate affected desulfurization rates

Natural Pigment Production by Monascus purpureus: Improving the yield in a bioreactor based on statistical analysis

AbstractDue to the especial properties such as high growth rates, easy extraction as well as high yields, using microorganisms in comparison to other sources is more chosen for pigment production. Pigments are used in food industries as natural colorants and preservatives, they also have pharmaceutical applications. In this study, fungus Monascus purpureus PTCC 5303 have been used to produce red, orange and yellow pigments. At first significant variables were screened based on plackett-Burman design and then the optimized value of two effectivefactors such as yeast extract and K2HPO4 concentrations wasoptimized byresponse surface method. Optimal levels of factors were found to be 2/75 g/L yeast extract and1/5 g/LK2HPO4 respectively. Antimicrobial activity of pigments was evaluated on Gram-positive foodborne bacteria under optimal conditionswhich resultsshowed inhibitory effects. Moreover Pigments production at optimal conditions in a bioreactor was evaluatedand the rate of production of red, orange and yellow pigments, 2.05, 1.55 and 0.78 (ODU/ml) were observed respectively.  </div

Simulation and evaluation of the performance of various sensor-sensing silicones to detect methane-soluble in fermentation process

At present, spectrometric chromatography are used to methane in the fermentation process, but the use of off-line mass spectrometry requires the sampling and maintenance of the solution. Silicon membrane-based gas sensors are designed and used to detect methane based on this principle. The simulation of this sensor was carried out using COMSOL Multhiphysics (CM) 5.2 A software in 3D. Input gas helium was applied at three values of 40, 50 and 60 ml/min. Also, silicon tubes with lengths of 5, 10 and 15 cm and in three diameters of 0.05, 0.05, and 0.25 cm were investigated. The shortest response time from the sensor simulation is 10% compared to the results of the experimental at 1.6 minutes. The shear stresses, the effect of inlet gas velocity, flow pressure and fluid concentration in this study were compared. All result showed that the silicon membrane-based have been best absorbent for gas specially Methane

Construction and Characterization of a New Recombinant Vector to Remove Sulfate Repression of dsz Promoter Transcription in Biodesulfurization of Dibenzothiophene

Biodesulfurization (BDS) is an environmentally friendly desulfurizing process with the potential of replacing or adding to the current expensive technologies for sulfur removal from fossil fuels. The BDS, however, still suffers from low biocatalyst activity. One reason is repression of dsz promoter transcription in presence of inorganic sulfate that impedes translation of Dsz enzymes required for desulfurization pathway. One approach to solve this problem is replacing the native promoter with a new promoter that is no longer repressed. In this study, dsz genes from desulfurizing strain Rhodococcus sp. FUM94 was cloned in an alkane responsive promoter, pCom8, and expressed in Escherichia coli BL21 (DE3) as a host. The recombinant was not susceptible to inorganic sulfate in the culture medium. Desulfurizing activity of recombinant strain versus wild type indicated that in a sulfate containing medium, BDS yield of recombinant increased from 16.0% ± 0.9 to 34.0% ± 1.9% when dibenzothiophene (DBT) concentration (dissolved in ethanol) increased from 25 to 100 ppm. Also, 2-hydroxy biphenyl (2-HBP) production rate improved 8.5-fold (from 0.302 ± 0.020 to 2.57 ± 0.14 mmol 2-HBP (kg DCW)-1 h-1) at the same DBT concentration range. This is while no 2-HBP production was detected in FUM94 biphasic reaction. In a sulfate-free medium, wild type strain demonstrated desulfurization activity, but decreasing with the increase of DBT concentration dissolved in n-tetradecane. Whereas, the recombinant strain demonstrated increasing desulfurizing activity in a sulfate-containing high DBT concentration environment. Overall, the result of this molecular manipulation can be considered as a step forward toward commercialization of BDS technology

Antifouling potential of enzymes applied to reverse osmosis membranes

Many companies in the food industry apply reverse osmosis (RO) membranes to ensure high-quality reuse of water. Biofouling is however, a common, recalcitrant and recurring problem that blocks transport over membranes and decreases the water recovery. Microorganisms adhering to membranes may form biofilm and produce an extracellular matrix, which protects against external stress and ensures continuous attachment. Thus, various agents are tested for their ability to degrade and disperse biofilms. Here, we identified industrially relevant bacterial model communities that form biofilms on RO membranes used for treating process water before reuse. There was a marked difference in the biofilm forming capabilities of bacteria isolated from contaminated RO membranes. One species, Raoultella ornithinolytica, was particularly capable of forming biofilm and was included in most communities. The potential of different enzymes (Trypsin-EDTA, Proteinase K, α-Amylase, β-Mannosidase and Alginate lyase) as biofouling dispersing agents was evaluated at different concentrations (0.05 U/ml and 1.28 U/ml). Among the tested enzymes, β-Mannosidase was the only enzyme able to reduce biofilm formation significantly within 4 h of exposure at 25 °C (0.284 log reduction), and only at the high concentration. Longer exposure duration, however, resulted in significant biofilm reduction by all enzymes tested (0.459–0.717 log reduction) at both low and high concentrations. Using confocal laser scanning microscopy, we quantified the biovolume on RO membranes after treatment with two different enzyme mixtures. The application of proteinase K and β-Mannosidase significantly reduced the amount of attached biomass (43% reduction), and the combination of all five enzymes showed even stronger reducing effect (71% reduction). Overall, this study demonstrates a potential treatment strategy, using matrix-degrading enzymes for biofouled RO membranes in food processing water treatment streams. Future studies on optimization of buffer systems, temperature and other factors could facilitate cleaning operations based on enzymatic treatment extending the lifespan of membranes with a continuous flux