Extensive reuse of soda-lime waste glass in fly ash-based geopolymers

The possibility of extensive incorporation of soda-lime waste glass in the synthesis of fly ash-based geopolymers was investigated. Using waste glass as silica supplier avoids the use of water glass solution as chemical activator. The influence of the addition of waste glass on the microstructure and strength of fly ash-based geopolymers was studied through microstructural and mechanical characterization. Leaching analyses were also carried out. The samples were developed changing the SiO2/Al2O3 molar ratio and the molarity of the sodium hydroxide solution used as alkaline activator. The results suggest that increasing the amount of waste glass as well as increasing the molarity of the solution lead to the formation of zeolite crystalline phases and an improvement of the mechanical strength. Leaching results confirmed that the new geopolymers have the capability to immobilize heavy metal ions

NMR Studies on Structure and Dynamics of the Monomeric Derivative of BS-RNase: New Insights for 3D Domain Swapping

Three-dimensional domain swapping is a common phenomenon in pancreatic-like ribonucleases. In the aggregated state, these proteins acquire new biological functions, including selective cytotoxicity against tumour cells. RNase A is able to dislocate both N- and C-termini, but usually this process requires denaturing conditions. In contrast, bovine seminal ribonuclease (BS-RNase), which is a homo-dimeric protein sharing 80% of sequence identity with RNase A, occurs natively as a mixture of swapped and unswapped isoforms. The presence of two disulfides bridging the subunits, indeed, ensures a dimeric structure also to the unswapped molecule. In vitro, the two BS-RNase isoforms interconvert under physiological conditions. Since the tendency to swap is often related to the instability of the monomeric proteins, in these paper we have analysed in detail the stability in solution of the monomeric derivative of BS-RNase (mBS) by a combination of NMR studies and Molecular Dynamics Simulations. The refinement of NMR structure and relaxation data indicate a close similarity with RNase A, without any evidence of aggregation or partial opening. The high compactness of mBS structure is confirmed also by H/D exchange, urea denaturation, and TEMPOL mapping of the protein surface. The present extensive structural and dynamic investigation of (monomeric) mBS did not show any experimental evidence that could explain the known differences in swapping between BS-RNase and RNase A. Hence, we conclude that the swapping in BS-RNase must be influenced by the distinct features of the dimers, suggesting a prominent role for the interchain disulfide bridges

Continuous succinic acid fermentation by Actinobacillus succinogenes in a packed-bed biofilm reactor

Background: Succinic acid is one of the most interesting platform chemicals that can be produced in a biorefinery approach. In this study, continuous succinic acid production by Actinobacillus succinogenes fermentation in a packed-bed biofilm reactor (PBBR) was investigated. Results: The effects of the operating conditions tested, dilution rate (D), and medium composition (mixture of glucose, xylose, and arabinose - that simulate the composition of a lignocellulosic hydrolysate) - on the PBBR performances were investigated. The maximum succinic acid productivity of 35.0 g L-1 h-1 and the maximum SA concentration were achieved at a D = 1.9 h-1. The effect of HMF and furfural on succinic acid production was also investigated. HMF resulted to reduce succinic acid production by 22.6%, while furfural caused a reduction of 16% in SA production at the same dilution rate. Conclusion: Succinic acid production by A. succinogenes fermentation in a packed-bed reactor (PBBR) was successfully carried out for more than 5 months. The optimal results were obtained at the dilution rate 0.5 h-1: 43.0 g L-1 of succinic acid were produced, glucose conversion was 88%; and the volumetric productivity was 22 g L-1 h-1.</p

Efficient succinic acid production from high-sugar-content beverages by Actinobacillus succinogenes

This study presents the production of succinic acid (SA) by Actinobacillus succinogenes using high-sugar-content beverages (HSCBs) as feedstock. The aim of this study was the valorization of a by-product stream from the beverage industry for the production of an important building block chemical, such as SA. Three types of commercial beverages were investigated: fruit juices (pineapple and ace), syrups (almond), and soft drinks (cola and lemon). They contained mainly glucose, fructose, and sucrose at high concentration—between 50 and 1,000 g/L. The batch fermentation tests highlighted that A. succinogenes was able to grow on HSCBs supplemented with yeast extract, but also on the unsupplemented fruit juices. Indeed, the bacteria did not grow on the unsupplemented syrup and soft drinks because of the lack of indispensable nutrients. About 30–40 g/L of SA were obtained, depending on the type of HSCB, with yield ranging between 0.75 and 1.00 gSA/gS. The prehydrolysis step improved the fermentation performance: SA production was improved by 6–24%, depending on the HSCB, and sugar conversion was improved of about 30–50%.</p

Fly-Ash-Based Geopolymers: How the Addition of Recycled Glass or Red Mud Waste Influences the Structural and Mechanical Properties

One of the main advantages of geopolymer technology is its capability to accommodate several types of waste that would otherwise be disposed of in landfills in the production of geopolymer materials. This study investigates the possibility of substituting proportions of fly ash, normally used for the synthesis of geopolymers, with recycled glass and red mud waste. Compressive and flexural strength testing, fracture toughness determination, SEM and FTIR analyses were performed. The results show that the compressive strength decreases as the amount of glass in the geopolymer increases; on the other hand, the addition of red mud seems to improve the mechanical behavior. Moreover,onsubstitutionofflyashwithglassandredmud,thegeopolymerdemonstratesasimilarperformancein termsoffracturetoughnessandflexuralstrengthproperties.Theresultsconfirmthatredmudandwasteglasshave the potential to partially replace fly ash in geopolymer synthesis, opening thus the possibility of using geopolymer technologytoreusesuchresiduesintechnicalmaterials

MOESM1 of Continuous succinic acid fermentation by Actinobacillus succinogenes in a packed-bed biofilm reactor

Additional file 1: Figure S1. Biofilm of A. succinogenes. a) at the end of the start-up phase; b) after 5 months of continuous operation. Figure S2. Time-course profiles of the fermentation results during the production phase from glucose. a Glucose (▼) and cell concentration (○) and dilution rate (dashed line); b succinic (∆), acetic (●) and formic (□) acid concentration and dilution rate. Figure S3. Time-course profiles of the fermentation results during the adaptation phase from glucose to xylose. a Glucose (▼), xylose (■) and cell concentration (○); b succinic (∆), acetic (●), and formic (□) acid concentration and xylose percentage (dashed line) in the medium. The dilution rate was set to 1.24 h−1. Figure S4. Time-course profiles of the fermentation results during the production phase from xylose. a Xylose (▼) and cell concentration (○) and dilution rate (dashed line); b succinic (∆), acetic (●), and formic (□) acid concentration and dilution rate. Figure S5. Time-course profiles of the fermentation results during the production phase from GAX medium. a Sugars [glucose (▼), xylose (■), and arabinose (∇)] and cell concentration (○) and dilution rate (dashed line); b succinic (∆), acetic (●), and formic (□) acid concentration and dilution rate

The thyroid hormone T3 improves function and survival of rat pancreatic islets during in vitro culture

Ex vivo islet cell culture in the presence of stimulating factors prior to transplantation is considered a good strategy in contrast to the short conclusion of islets transplantation. Previously, we demonstrated how T3 can increase beta-cell function via specific activation of Akt; therefore we hypothesized that thyroid hormone T3 can be considered a promising candidate for the in vitro expansion of islet cell mass. Rat pancreatic islets have been isolated by the collagenase digestion and cultured with or without the presence of the thyroid hormone T3 10(-7) M. Islets viability has been evaluated by the use of two different dyes, one cell-permeable green fluorescent dye and propidium iodide, and by the analysis of core cell damage upcoming. Moreover, islets function has been evaluated by insulin secretion. The ability of beta-cells to counteract apoptosis induced by streptozotocin has been analyzed by TUNEL assay. We demonstrated that treatment of primary cultures of rat pancreatic islets with T3 results in augmented beta-cell vitality with an increase of their functional properties. In addition, a sensible reduction of the core cell damage has been observed in the T3 treated islets, suggesting the preservation of the beta-cells integrity during the culture period. Nonetheless, the insulin secretion is sensibly augmented after T3 stimulation. The strong increment shown in Akt activation suggests the involvement of this pathway in the observed phenomena. In conclusion we indicate T3 as a good factor to improve ex vivo islets cell culture