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The aim of this work is a green synthesis of gold nanoparticles using the aqueous extract of Anthriscus sylvestris, Ferula gummosa, and Achillea eriohora leaf and stems as the reducing agents. The effects of reducing agent concentration in the reaction mixture and temperature on the size of the gold nanotriangles were studied. The nanoparticles were characterized using UV–Vis spectroscopy, XRD, and SEM. XRD studies show that the particles are crystalline in the cubic phase. However, the reduction of gold ions by plant extracts resulted in the formation of spherical gold nanoparticles with diameters from 18 to 56 nm.

In this study, ectoine is produced by Streptomyces. sp IBRC-M PTCC 10615. Fermentation parameters such as flow regime, gas hold up, mass transfer coefficient, and mixing time were optimized by statistical analysis. Streptomyces. sp produced a maximal ectoine concentration of 270 mmol/kg at optimal conditions of ectoine and L-aspartic acid. Also, the amount of mass transfer, gas hold up, and mixing time were determined 0,41/s ,0.3, and 40 s, respectively. The amount of ectoine was measured by HPLC. Furthermore, Molecular Dynamics (MD) simulation was used for studying the solubility of ectoine in aqueous media. Equilibrium data such as temperature, potential energy, and volume graphs showed that the solubility of ectoine is 25%more than glycerol. Also, all the achieving graphs from the equilibrium of simulation were confirmed the appropriate structure of the system.

Recently, many economic studies of poly(3-hydroxybutyrate) PHB production on an industrial scale, and the impact of replacing petrochemical polymers by PHB were carried out, clearly indicating that the most crucial factors to reduce the cost of producing biopolymers are allotted to the application of microbial production strains capable of high productivity in inexpensive carbon sources, high cell density cultivation methods, cheap yet effective methods for the extraction of PHB and other polyhydroxyalkanoates (PHAs), and gene transfer from bacteria to plants. We present current strategies to reduce the production price of biological PHA. Because an important part of the PHA production cost is related to the cost of carbon source, the article focuses on the use of natural gas as an inexpensive and readily available C1-carbon source. Since the first and foremost point in PHA production is biomass growth, we discuss different types of bioreactors to be potentially used for efficient biomass production from natural gas, which facilitates the subsequent selection of the ideal bioreactor for PHA production from this substrate. Nowadays, process simulation software can be used as a powerful tool for analysis, optimization, design, and scale up of bioprocesses. Controlling the process design by in silico simulations instead of performing an excessive number of lab-scale experiments to optimize various factors to save in time, material and equipment. Simulation of PHA production processes to find the optimal conditions can play a decisive role in increasing the production efficiency. Computational fluid dynamics and mathematical modeling helps us to achieve a better understanding of the role of different nutrients, flow parameters of gaseous substrates, efficient feeding strategies, etc. This finding leads to higher productivity by prediction of parameters e.g. nutrient supply and biomass concentration time profile and their respective yields.

The mixing behavior of the gas-liquid phase in three loop bioreactors was investigated. A gas-induced External Airlift Loop Bioreactor (EALB), a forced-liquid Vertical Tubular Loop Bioreactor (VTLB) and a forced-liquid Horizontal Tubular Loop Bioreactor (HTLB) were used for mixing studies as well as biomass production from natural gas. The effect of design parameters, riser to downcomer cross sectional area ratio (Ar/Ad ), height to diameter ratio (H/D), length to diameter ratio (L/D) and volume of gas-liquid separator (S); as well as operational parameters, i.e. superficial gas velocity (UsG ) and superficial liquid velocity (UsL) on mixing time were studied. It was found that liquid circulation (pumping) had an important effect on mixing time. VTLB, because of providing an effective countercurrent flow between gas and liquid streams, demonstrated the best mixing time performance. HTLB, as the second, provides a moderated mixing time output. EALB, since circulates no forced liquid, presents less mixing ability (gas moves liquid). It was observed from experimental results that mostly superficial gas velocity has an obvious effect on EALB. Accordance to mixing time data, a region that was independent on bioreactor type was explored that happened in high gas superficial velocity. In that zone, mixing time was not reliant on bioreactor variety and varies with the variation of operational and design parameters only. Some empirical correlations for mixing time in terms of Ar/Ad, H/D, L/D, UsG, UsL and volume of gas-liquid separator were obtained and expressed separately which can be used for design and scale up. The best biomass production occurred in the VTLB for gas mixture of 40% methane and 60% air.

The performance of a forced-liquid Vertical Tubular Loop Bioreactor (VTLB), a forced-liquid Horizontal Tubular Loop Bioreactor (HTLB) and a gas-induced External Airlift Loop Bioreactor (EALB) were compared for production of biomass from natural gas. Hydrodynamic characteristics and mass transfer coefficients were determined as functions of design parameters, physical properties of gases as well as operational parameters. Moreover, energy consumption for different gas and liquid flow rates was studied. In the EALB, kinematic viscosity (υg) showed its significant role on mixing time, gas hold-up and kLa and the diffusion coefficient of gas in water (Dg) had a remarkable effect on kLa. It was observed from experimental results that the performance of the VTLB was the best for biomass production. Furthermore, the volumetric mass transfer coefficients for air and methane were determined at different geometrical and operational factors. New correlations for mixing time, gas hold-up and kLa were obtained and expressed separately. Also, the different ratios of methane and air were measured and compared for optimum growth in the VTLB, HTLB and EALB.

A dissolved methane sensor based on silicone tube was designed, constructed and optimized.The silicone tube diameter, silicone tube length and helium flow rate (as the carrier gas(were considered as process parameters to be optimized.A continuous stream of helium (50 mL/min) was directed through the tubing, sweeping out the dissolved methane which diffused through the walls of the tubing from the fermentation broth. The probe was made of silicone rubber tubing, 10 cm in length with inner and outer diameters of 0.25 cm and 0.35 cm, respectively (Detakta Company; NO. 02502). A semi-conductor methane gas sensor (Figaro TGS 2611) - which is highly sensitive and selective to methane gas - was used to measure the dissolved methane continuously. Henry’s law along with a special circuit experimental method was applied for calibration. The output concentration was displayed in mg/l (or ppm) of dissolved gas. The accuracy and response time of this system are ± 2 % and 2 minutes, respectively. Moreover, a control system was installed for recycling methane gas during fermentation