Xylanase Production by Penicillium citrinum in Laboratory-scale Stirred Tank Reactor

Xylanase constitutes an important class of hydrolases, and is used in numerous industrial applications. The aim of the present work was to study the production of xylanase from Penicillium citrinum MTCC 9620 in a 5 L stirred tank bioreactor. Effect of various process parameters; pH, temperature, aeration, agitation rates, substrate concentration, and, dissolved oxygen (DO) concentration on xylanase production were studied. Combination of all the optimized parameters resulted in 2.5 times higher enzyme activity as compared to the shake flask fermentation after 96 h. Effect of varying agitation and aeration on the volumetric mass transfer coefficient (KLa) was determined. It revealed that KLa is influenced by both aeration and agitation. Growth kinetics of P. citrinum MTCC 9620 in bioreactor was studied using Monod, Moser, Contois and Edward equation. Based on R2, SE and pattern of residuals, the microbial growth kinetics of P. citrinum MTCC 9620 was effectively represented by Moser equation

Optimization of Xylanase Production from Penicillium citrinum in Solid-State Fermentation

Solid-state fermentation of sugarcane bagasse by Penicillium citrinum MTCC 2553 was optimized to maximize the yield of xylanase. Preliminary experiments carried out with various lignocellulosic materials revealed sugarcane bagasse to be the most suitable substrate for producing xylanase. Response surface methodology was used in the optimization. Xylanase activity was maximized in a 5-day batch fermentation carried out under the following conditions: a substrate-to-moisture ratio of 1:5 by mass, an initial pH of 7.0 and an incubation temperature of 30 °C. Under the optimal conditions, the final activity of xylanase was 1645 U g–1 of dry substrate. Xylanase was recovered from an extract of the fermented solids by ammonium sulfate precipitation. The crude enzyme was further purified by dialysis. The activity of the enzyme was enhanced in the presence of Na+, Mg2+, Mn2+, Fe3+, Zn2+, Cu2+, Co2+ and Tween 80. The enzyme was inhibited by Hg2+, Ca2+ and the chelating agent ethylene diamine tetra acetic acid (EDTA)

On-water surface synthesis of crystalline, few-layer two-dimensional polymers assisted by surfactant monolayers

Despite rapid progress in recent years, it has remained challenging to prepare crystalline two-dimensional polymers. Here, we report the controlled synthesis of few-layer two-dimensional polyimide crystals on the surface of water through reaction between amine and anhydride monomers, assisted by surfactant monolayers. We obtained polymers with high crystallinity, thickness of ~2 nm and an average crystal domain size of ~3.5 μm2. The molecular structure of the materials, their grain boundaries and their edge structures were characterized using X-ray scattering and transmission electron microscopy techniques. These characterizations were supported by computations. The formation of crystalline polymers is attributed to the pre-organization of monomers at the water–surfactant interface. The surfactant, depending on its polar head, promoted the arrangement of the monomers—and in turn their polymerization—either horizontally or vertically with respect to the water surface. The latter was observed with a surfactant bearing a carboxylic acid group, which anchored amine monomers vertically through a condensation reaction. In both instances, micrometre-sized, few-layer two-dimensional polyamide crystals were grown

Highly Crystalline and Semiconducting Imine-Based Two-Dimensional Polymers Enabled by Interfacial Synthesis

Single‐layer and multi‐layer 2D polyimine films have been achieved through interfacial synthesis methods. However, it remains a great challenge to achieve the maximum degree of crystallinity in the 2D polyimines, which largely limits the long‐range transport properties. Here we employ a surfactant‐monolayer‐assisted interfacial synthesis (SMAIS) method for the successful preparation of porphyrin and triazine containing polyimine‐based 2D polymer (PI‐2DP) films with square and hexagonal lattices, respectively. The synthetic PI‐2DP films are featured with polycrystalline multilayers with tunable thickness from 6 to 200 nm and large crystalline domains (100–150 nm in size). Intrigued by high crystallinity and the presence of electroactive porphyrin moieties, the optoelectronic properties of PI‐2DP are investigated by time‐resolved terahertz spectroscopy. Typically, the porphyrin‐based PI‐2DP 1 film exhibits a p‐type semiconductor behavior with a band gap of 1.38 eV and hole mobility as high as 0.01 cm2 V−1 s−1, superior to the previously reported polyimine based materials

<span style="font-size:11.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:simsun;mso-bidi-font-family:mangal;="" mso-ansi-language:en-gb;mso-fareast-language:zh-cn;mso-bidi-language:hi"="" lang="EN-GB">Isolation, Screening and Optimization of Xylanase Production in Submerged Fermentation Using <i>P.citrinum</i>.</span>

400-405Cellulase free xylanase is one of the most important upcoming enzyme having industrial application in chemical, biochemical, pharmaceutical and food industry. In the present study, a soil isolate was found to be promising for xylanase production. Biochemical identification tests, Scanning Electron Microscopy (SEM) and 16S rRNA sequencing identified the organism Penicillium citrinum MTCC 9620. Later on, optimization of media composition and environmental factors were investigated. Temperature, pH, agitation speed, carbon sources, nitrogen sources, inoculum concentration, and additives were optimized on the basis of xylanase yield, dry cell weight, extracellular protein content, sugar consumption etc. Optimized media produced 138.73 U/mL xylanase at 120 h (30°C). The purified xylanase was found to have molecular weight approximately 29 KDa