S. Chatterjee

Food waste biorefinery: Sustainable strategy for circular bioeconomy

Enormous quantity of food waste (FW) is becoming a global concern. To address this persistent problem, sustainable interventions with green technologies are essential. FW can be used as potential feedstock in biological processes for the generation of various biobased products along with its remediation. Enabling bioprocesses like acidogenesis, fermentation, methanogenesis, solventogenesis, photosynthesis, oleaginous process, bio-electrogenesis, etc., that yields various products like biofuels, platform chemicals, bioelectricity, biomaterial, biofertilizers, animal feed, etc can be utilized for FW valorisation. Integrating these bioprocesses further enhances the process efficiency and resource recovery sustainably. Adapting biorefinery strategy with integrated approach can lead to the development of circular bioeconomy. The present review highlights the various enabling bioprocesses that can be employed for the generation of energy and various commodity chemicals in an integrated approach addressing sustainability. The waste biorefinery approach for FW needs optimization of the cascade of the individual bioprocesses for the transformation of linear economy to circular bioeconomy.

Microbial lipid production by Cryptococcus curvatus from vegetable waste hydrolysate

This study primarily evaluated the effect of pre-treatment on release of reducing sugars (RS) from vegetable waste (VW). Different acids and alkalis viz., H2SO4, HCl, HNO3, H3PO4, NaOH and KOH were evaluated at varied concentration (0.5, 1.0, 1.5 and 2.0%) for pretreatment. The highest RS yield of 472.36 ± 1.89 g/l and 439.13 ± 1.04 g/l was obtained with 1.5% H2SO4 and 2% HCl respectively. Secondly, pre-treated vegetable waste hydrolysates (PT-VWH) were evaluated for yeast fermentation using Cryptococcus curvatus MTCC 2698 for lipid production. Maximum biomass (9.46 ± 0.1 g/l and 8.12 ± 0.1 g/l) and lipid (28.3 ± 0.5% and 26 ± 0.5%) was obtained with 1.5% H2SO4 PT-VWH and 2% HCl PT-VWH respectively. The FAME profiling revealed the predominance of palmitic, stearic, oleic and linoleic acid. The presence of these fatty acids in majority has beneficial effect on the biodiesel quality.

A 2D position sensitive germanium detector for spectroscopy and polarimetry of high-energetic x-rays

We report on a first prototype 2D μ-strip germanium detector, developed at IKP-Julich, and its performance test at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. Beside an accurate determination of the detector response function, the polarization sensitivity has been addressed in this study. For this purpose photon beams at energies of 60 keV and 210 keV have been used.

Recent Developments for the Investigation of Ground-State Transitions in Heavy One-Electron Ions

Accurate investigations of the structure of one- and few-electron ions in the high-Z regime provide unique possibilities for testing fundamental theories underlaying our present understanding of of the physics of extremely electro-magnetic strong fields. In this review, we concentrate on x-ray spectroscpic investigations of the ground-state transition energies in H-like uranium (heaviest stable element available) by using the intense beams of cooled heavy ions provided by the storage ring ESR at GSI. Such experiments allow for a precise study of the ground-state binding-energies in high-Z H-like ions where relativistic and QED effects are strongest. The most recent experiment is presented where the deceleration capability of the ESR storage ring was exploited for x-ray spectroscopy at the ESR electron cooler. In addition, we discuss the ongoing developments for a new generation of ground-state Lamb shift experiments aiming on a precision of 1 eV or even better. In particular, emphasis will be given to the dedicated crystal spectrometer (FOCAL) in combination with state of the art 2D position-sensitive solid state detectors, allowing for energy and time resolved x-ray imaging.

Observation of enhancement in K-shell radiative recombination of U92+ ions with cooling electrons

The observation of the enhancement of radiative recombination (RR) into the K-shell for U92+ ions interacting with cooling electrons in x-ray RR experiment performed at the ESR storage ring is reported. From the measured intensities of K-RR x-rays for the electron relative energies in the range 0-1000 meV a clear indication of the recombination enhancement, with respect of the fully relativistic RR calculations, was found for the K-shell for the zero relative electron energy. This results add new aspects to existing interpretations of the enhancement effect emphasizing a role of recombination into high Rydberg states.

Recent experimental developments for the Lamb shift investigation in heavy ions

The latest commissioning experiment of a two arm transmission crystal x-ray spectrometer along with high-performance position-sensitive microstrip germanium detectors is presented. The goal of the experiment was to observe with high resolution the Ly-α-transitions of H-like Pb81+produced in collisions with Kr atoms. Due to a photon e.ciency of only 10−8 the position sensitivity as well as the energy and time resolution of segmented solid state Germanium detectors are absolutely essential for experiments using crystal x-ray spectrometers dealing with beams of heavy ions. A detector system with the desired properties has become available through a collaboration with the Forschungszentrum Julich.

Enhanced radiative recombination of U92+ ions with cooling electrons for the K-shell

Observed enhancement of K-shell radiative recombination (RR) of bare uranium ions with cooling electrons is interpreted in terms of of distant transverse collisions in magnetized electron-cooler plasma described within the semiclassical geometrical model (SGM), which was recently proposed. The Monte Carlo simulations based on the proposed approach explains the enhancement measured in RR of U92+ ions with cooling electrons for the K-shell.