Optimization of capsaicin acylase production from Streptomyces mobaraensis in bench-top fermenter

Capsaicin, the major pungent principle in hot pepper fruit, can be hydrolyzed enzymatically to vanillylamine (a natural precursor of vanillin) using a specific acylase from Streptomyces mobaraensis. Production of this enzyme using strain DSM40847 was studied under batch fermentation conditions in stirred tank (STR) and airlift (AR) bioreactors. The process performance in both fermentation devices was different with respect to biomass, enzyme concentration and specific yield (enzyme activity/biomass content); in particular the specific yield was lower in the AR (5.7 mU/g of biomass) than in the STR (6.25 mU/g of biomass). Experiments carried out in STR bioreactors at controlled (DO = 20% of saturation) and uncontrolled dissolved oxygen concentration, and at constant stirrer speeds (300, 450 and 600 rpm) demonstrated that the DO level has no remarkable effect on the production of the capsaicin-hydrolyzing enzyme, which is mainly produced in a cell-associated

Selection of Co-Substrate and Aeration Conditions for Vanillin Production by Escherichia coli JM109/pBB1

Yeast extract, Luria-Bertani medium and tryptone were tested as co-substrates for vanillin production from ferulic acid by resting cells of Escherichia coli JM109/pBB1. Yeast extract proved to be the best component for sustaining such a bioconversion, which is not self-sustained from the bioenergetic point of view. Tests were also performed under variable aeration conditions by simultaneously varying the ratio of medium to vessel volume and the agitation speed. The results of these tests suggest that, under excess aeration, a non-specific oxidase activity was very likely responsible for the oxidation of a significant portion of vanillin to vanillic acid, thus reducing the vanillin yield

Improvement of the extraction method of faint signals in γ -activity measurements of meteorites

The final publication is available at Springer via https://doi.org/10.1140/epjp/i2017-11556-yAt the underground laboratory of Monte dei Cappuccini (OATo-INAF) in Torino (Italy) we set up selective HPGe-NaI(Tl) spectrometers for measurements of cosmogenic radioisotopes in meteorites in order to study centennial-scale modulation of solar activity. 44 Ti is a suitable proxy for this timescale, but its detection is difficult due to the strong interference by naturally occurring 214 Bi. In order to optimize the extraction of the 44 Ti signal, we have developed software procedures specifically designed to improve selectivity of the Ge-NaI detectors coincidence

Long-term heliomagnetic field variation based on cosmogenic 44Ti in meteorites

Reconstructions of the heliospheric magnetic field (HMF) in the past centuries are mainly based on the analysis of sunspot activity, geomagnetic data or on measurement of cosmogenic radioisotopes stored in terrestrial reservoirs (tree rings and ice cores). There are, however, significant discrepancies among the results obtained by various techniques using different proxies of solar magnetic activity. In this work, new results obtained from a unique approach based on the measurement of the cosmogenic 44Ti activity detected in meteorites are presented and compared with the most recent reconstructions of the near-Earth HMF strength. The very low level of 44Ti activity in several meteorites fallen in the last 250 years was determined by using gamma-ray spectrometers (HPGe+NaI) located in the underground laboratory of Monte dei Cappuccini (INAF-OATo) in Torino, Italy. This approach, specifically designed to overcome the main problems affecting other methods, yields a powerful independent tool to reconstruct the long-term evolution of the HMF through the last two and a half centuries

Simulations studies for the Mini-EUSO detector

Mini-EUSO is a mission of the JEM-EUSO program flying onboard the International Space Station since August 2019. Since the first data acquisition in October 2019, more than 35 sessions have been performed for a total of 52 hours of observations. The detector has been observing Earth at night-time in the UV range and detected a wide variety of transient sources all of which have been modelled through Monte Carlo simulations. Mini-EUSO is also capable of detecting meteors and potentially space debris and we performed simulations for such events to estimate their impact on future missions for cosmic ray science from space. We show here examples of the simulation work done in this framework to analyse the Mini-EUSO data. The expected response of Mini-EUSO with respect to ultra high energy cosmic ray showers has been studied. The efficiency curve of Mini-EUSO as a function of primary energy has been estimated and the energy threshold for Cosmic Rays has been placed to be above 10^{21} eV. We compared the morphology of several transient events detected during the mission with cosmic ray simulations and excluded that they can be due to cosmic ray showers. To validate the energy threshold of the detector, a system of ground based flashers is being used for end-to-end calibration purposes. We therefore implemented a parameterisation of such flashers into the JEM-EUSO simulation framework and studied the response of the detector with respect to such sources

Pre-flight qualification tests of the Mini-EUSO telescope engineering model

International audienceMini-EUSO is part of the JEM-EUSO program and operates on board the International Space Station (ISS). It is a UV-telescope with single-photon counting capability looking at nighttime downwards to the Earth through a nadir-facing UV-transparent window. As part of the pre-flight tests, the Mini-EUSO engineering model, a telescope with 1/9 of the original focal surface and a lens of 2.5 cm diameter, has been built and tested. Tests of the Mini-EUSO engineering model have been made in laboratory and in open-sky conditions. Laboratory tests have been performed at the TurLab facility, located at the Physics Department of the University of Turin, equipped with a rotating tank containing different types of materials and light sources. In this way, the configuration for the observation of the Earth from space was emulated, including the Mini-EUSO trigger schemes. In addition to the qualification and calibration tests, the Mini-EUSO engineering model has also been used to evaluate the possibility of using a JEM-EUSO-type detector for applications such as observation of space debris. Furthermore, observations in open-sky conditions allowed the studies of natural light sources such as stars, meteors, planets, and artificial light sources such as airplanes, satellites reflecting the sunlight, and city lights. Most of these targets could be detected also with Mini-EUSO. In this paper, the tests in laboratory and in open-sky conditions are reported, as well as the obtained results. In addition, the contribution that such tests provided to foresee and improve the performance of Mini-EUSO on board the ISS is discussed