Isolation of thermotolerant,halotolerant, facultative biosurfactant-producing bacteria

Several facultative bacterial strains tolerant to high temperature and salinity were isolated from the oil reservoir brines of an Iranian oil field (Masjed-I Soleyman). Some of these isolates were able to grow up to 60°C and at high concentration of NaCl (15% w/v). One of the isolates grew at 40°C, while it was able to grow at 15% w/v NaCl. Tolerances to NaCl levels decreased as the growth temperatures were increased. Surfactant production ability was detected in some of these isolates. The use of biosurfactant is considered as an effective mechanism in microbial-enhanced oil recovery processes detected in some of these isolates. The surfactant producers were able to grow at high temperatures and salinities to about 55°C and 10% w/v, respectively. These isolates exhibited morphological and physiological characteristics of the Bacillus genus. The partial sequencing of the 16S ribosomal deoxyribonucleic acid gene of the selected isolates was assigned them to Bacillus subtilis group. The biosurfactant produced by these isolates caused a substantial decrease in the surface tension of the culture media to 26.7 mN/m. By the use of thin-layer chromatography technique, the presence of the three compounds was detected in the tested biosurfactant. Infrared spectroscopy and ¹H nuclear magnetic resonance analysis were used, and the partial structural characterization of the biosurfactant mixture of the three compounds was found to be lipopeptidic in nature. The possibility of use of the selected bacterial strains reported, in the present study, in different sectors of the petroleum industry has been addressed.     

Kinetic model-based feed-forward controlled fed-batch fermentation of Lactobacillus rhamnosus for the production of lactic acid from Arabic date juice

Arabic date is overproduced in Arabic countries such as Saudi Arabia and Iraq and is mostly composed of sugars (70–80 wt%). Here we developed a fed-batch fermentation process by using a kinetic model for the efficient production of lactic acid to a high concentration from Arabic date juice. First, a kinetic model of Lactobacillus rhamnosus grown on date juice in batch fermentation was constructed in EXCEL so that the estimation of parameters and simulation of the model can be easily performed. Then, several fed-batch fermentations were conducted by employing different feeding strategies including pulsed feeding, exponential feeding, and modified exponential feeding. Based on the results of fed-batch fermentations, the kinetic model for fed-batch fermentation was also developed. This new model was used to perform feed-forward controlled fed-batch fermentation, which resulted in the production of 171.79 g l^?1 of lactic acid with the productivity and yield of 1.58 and 0.87 g l^?1 h^?1, respectively.     

Dissolved oxygen concentration regulates human hepatic organoid formation from pluripotent stem cells in a fully controlled bioreactor

Developing technologies for scalable production of human organoids has gained increased attention for “organoid medicine” and drug discovery. We developed a scalable and integrated differentiation process for generation of hepatic organoid from human pluripotent stem cells (hPSCs) in a fully controlled stirred tank bioreactor with 150 ml working volume by application of physiological oxygen concentrations in different liver tissue zones. We found that the 20–40% dissolved oxygen concentration [DO] (corresponded to 30–60 mmHg pO₂ within the liver tissue) significantly influences the process outcome via regulating the differentiation fate of hPSC aggregates by enhancing mesoderm induction. Regulation of the [DO] at 30% DO resulted in efficient generation of human fetal-like hepatic organoids that had a uniform size distribution and were comprised of red blood cells and functional hepatocytes, which exhibited improved liver-specific marker gene expressions, key liver metabolic functions, and, more important, higher inducible cytochrome P450 activity compared to the other trials. These hepatic organoids were successfully engrafted in an acute liver injury mouse model and produced albumin after implantation. These results demonstrated the significant impact of the dissolved oxygen concentration on hPSC hepatic differentiation fate and differentiation efficacy that should be considered ascritical translational aspect of established scalable liver organoid generation protocols for potential clinical and drug discovery applications.     

A new species and new records of Laelaspis Berlese (Acari, Laelapidae) from Iran

This paper reports on three species of mites of the genus Laelaspis in Iran - Laelaspis calidus Berlese from Pheidole pallidula, Laelaspis humeratus (Berlese) from Tetramorium caespitum and Laelaspis dariusi Joharchi & Jalaeian, sp. n. fromsoil. The new species is described and illustrations provided.     

Molecular and biochemical mechanisms of human iris color: A comprehensive review

Eye color is determined as a polymorphism and polygenic trait. Brown is the most common eye color in the world, accounting for about 79%, blue eye color for about 8–10%, hazel for 5%, and green for 2%. Rare-colored eyes include gray and red/violet. Different factors are involved in determining eye color. The two most important factors are the iris pigment and the way light is scattered from the iris. Gene expression determines the iris pigmentation and how much melanin is present in the eye, which is the number of melanin subunits that identify eye color. The genes involved in the pigmentation of single-nucleotide polymorphism (SNP) have a significant role; and even some genes are included only in the eye color through SNP. MicroRNAs also affect melanocyte synthesis, which is usually affected by the downregulation of essential genes involved in pigmentation. In this study, we assess the biochemical pathways of melanin synthesis, and the role of each gene in this pathway also has been examined in the signaling pathway that stimulates melanin synthesis.     

Studies on the protective effects of caffeic acid and quercetin on chemical-induced hepatotoxicity in rodents.

Caffeic acid and quercetin, the well-known phenolic compounds widely present in the plant kingdom, were investigated for their possible protective effects against paracetamol and CCl4-induced hepatic damage. Paracetamol at the oral dose of 1 g/kg produced 100% mortality in mice while pretreatment of separate groups of animals with caffeic acid (6 mg/kg) and quercetin (10 mg/kg) reduced the death rate to 20% and 30%, respectively. Oral administration of sub-lethal dose of paracetamol (640 mg/kg) produced liver damage in rats as manifested by the significant (P<0.01) rise in serum levels of aminotransferases (aspartate transaminase (AST) and alanine transaminase (ALT)) compared to respective control values. The serum enzyme values were significantly (P<0.01) lowered on pretreatment of rats with either caffeic acid (6 mg/kg) or quercetin (10 mg/kg). Similarly, the hepatotoxic dose of CCl4 (1.5 ml/kg; orally) also raised significantly (P<0.05) the serum AST and ALT levels as compared to control values. The same dose of the caffeic acid and quercetin was able to prevent CCl4-induced rise in serum enzymes. Caffeic acid and quercetin also prevented the CCl4-induced prolongation in pentobarbital sleeping time confirming their hepatoprotectivity. These results indicate that caffeic acid and quercetin exhibited hepatoprotective activity possibly through multiple mechanisms.