Fermentation of date palm juice by curdlan gum production from Rhizobium radiobacter ATCC 6466™: Purification, rheological and physico-chemical characterization

The present study was undertaken to investigate the possibility of using date palm juice byproducts for curdlan production by Rhizobium radiobacter ATCC 6466™ in batch experiments. A number of operational parameters, namely pH value, temperature range, inoculum ratio, agitation speed, carbon concentration, nitrogen source, and fermentation time, were investigated in terms of their optimal values for as well as individual and synergistic effects on curdlan production. The findings indicated that the strain exhibited a high ability to use the natural substrate under investigation. A curdlan production yield of 22.83 g/l was obtained in 500-ml agitated flasks (50 ml) when the strain was cultivated in the optimal medium (pH, 7; ammonium sulphate concentration, 2 g/l; date glucose juice concentration, 120 g/l) operating at 30 °C with an inoculum ratio of 5 ml/100 ml, an agitation speed of 180 rpm, and a fermentation period of 51 h. The purified date byproducts-curdlan (DBP-curdlan) had a molecular weight of 180 kDa, a linear structure composed exclusively of β-(1,3)-glucosidic linkages, a melting temperature (T_m) and glass transition temperature (T_g) of 1.24 and −3.55 °C, respectively. The average measured heights of its molecules were noted to fluctuate between 14.1 ± 0.07 and 211.73 ± 0.6 μm.     

Selective recovery of lithium from Dead Sea end brines using UBK10 ion exchange resin

The Dead Sea, a live pool of minerals and elements, holds ~9% of the world's known lithium reserves. However, the low lithium concentrations (30–40 mg/L) in the end brine and the high divalent to lithium ratio (Mg⁺² + Ca⁺² to Li⁺) were obstacles that must be overcome to extract the lithium. In our previous work, lithium concentrations in the Dead Sea end brine were enriched by chemical precipitation up to 1700 mg/kg in the produced solid precipitate. The obtained precipitate was decomposed by double-distilled water, and about 66% of lithium was leached, producing an environmental liquor containing an elevated concentration of lithium. A sequential ion exchange technique was used to achieve selective lithium recovery in this study. The ability of the UBK 10 strong acid-type cation exchange resin (Na type) to remove lithium from simulated and environmental lithium-bearing solutions was investigated. Because of the complex matrix comprising components that may compete with lithium adsorption, a greater quantity of adsorbent was required to achieve the equilibrium state for the environmental solution (7 g) compared to (3.6 g) for the simulated solution. For both lithium-bearing solutions, the kinetics investigation revealed a pseudo-second-order tendency. The interfering capacity was determined to be 0.405, confirming the UBK 10 challenge to selective lithium adsorption. The divalent to lithium ratio was decreased by more than 50 times, yielding encouraging findings for extracting lithium from the low lithium—high divalent to lithium sophisticated Dead Sea end brines.     

A Clustering-based Approach for Balancing and Scheduling Bicycle-sharing Systems

This paper addresses an inventory regulation problem in bicycle sharingsystems. The problem is to balance a network consisting of a set of stations by using a single vehicle, with the aim of minimizing the weighted sum of the waiting times during which some stations remain imbalanced. Motivated by the complexity of this problem, we propose a two-stage procedure based on decomposition. First, the network is divided into multiple zones by using two different clustering strategies. Then, the balancing problem is solved in each zone. Finally, the order in which the zones must be visited is defined. To solve these problems, different algorithms based on approximate, greedy and exact methods are developed. The numerical results show the effectiveness of the proposed regulation methodology.