Federico Fontana

New evidence for nitrogen fixation within the Italian white truffle Tuber magnatum.

Diversity of nitrogen-fixing bacteria and the nitrogen-fixation activity was investigated in Tuber magnatum, the most well-known prized species of Italian white truffle. Degenerate PCR primers were applied to amplify the nitrogenase gene nifH from T. magnatum ascomata at different stages of maturation. Putative amino acid sequences revealed mainly the presence of Alphaproteobacteria belonging to Bradyrhizobium spp. and expression of nifH genes from Bradyrhizobia was detected. The nitrogenase activity evaluated by acetylene reduction assay was 0.5-7.5μmolC(2)H(4)h(-1)g(-1), comparable with early nodules of legumes associated with specific nitrogen-fixing bacteria. This is the first demonstration of nitrogenase expression gene and activity within truffle.

Physically informed signal processing methods for piano sound synthesis: a research overview

This paper reviews recent developments in physics-based synthesis of piano. The paper considers the main components of the instrument, that is, the hammer, the string, and the soundboard. Modeling techniques are discussed for each of these elements, together with implementation strategies. Attention is focused on numerical issues, and each implementation technique is described in light of its efficiency and accuracy properties. As the structured audio coding approach is gaining popularity, the authors argue that the physical modeling approach will have relevant applications in the field of multimedia communication.

Acidification of grape marc for alcoholic beverage production: Effects on indigenous microflora and aroma profile after distillation

Grappa is an Italian alcoholic beverage obtained from distillation of grape marc, the raw material derived from separation of must during the winemaking process. Marc is stored for a period lasting from few days to several weeks, when fermentation of residual sugars occurs mainly by yeast activity. Many distilleries have adopted different solutions to manage this critical phase in order to avoid spoilage microorganisms: marc acidification is the most widely diffused. In this work, Prosecco grape pomace was acidified with sulphuric acid (to pH 2.9) and stored, whereas non-acidified grape marc was used as control (pH 3.9). Samples for microbiological analysis were collected at the beginning of the storage period, after 15 and 43days. At the beginning of the ensilage (time T0) the indigenous microflora was represented both by yeasts and bacteria at a concentration of about 10(6)cfu/g. During the first 15days, when the fermentation generally takes place, yeast population grew considerably (up to 10(7)cfu/g) in acidified grape marc, where bacterial population was maintained at low levels. Moreover, yeast populations recovered at the three sampling times in both treated and untreated marc were genetically characterised. This analysis showed that the species succession lead to non-Saccharomyces species dominance (in particular Issatchenkia and Pichia genera) in both conditions although acidified marc showed a lower percentage of Saccharomyces at any sampling time analysed, this meaning that non-Saccharomyces species were favoured in this environment. Gas chromatographic analysis showed a remarkable change in the aromatic profile of distilled grape marcs at the end of the storage, thus evidencing that concentration of monitored volatile compounds usually produced by microflora was generally lowered by the acidification treatment. This work demonstrates for the first time the strong effect of a persistent acidification treatment both on the microbiota of grape pomace and on the aromatic profile of the distillate. Indeed, the lowering of the pH caused significant changes in yeast-bacteria populations ratio and in yeast species turnover. These microbiological changes determine an improvement of the aromatic profile of the distillate, due to the reduction of the main volatile products associated with potential off-flavours.

Effects of yeast inoculation on volatile compound production by grape marcs

Grape marcs are a by-product of winemaking that can be used for production of Grappa, a traditional Italian spirit. This plant material needs to undergo a fermentation process before distillation to allow production of ethanol from residual sugar and volatile aromatic compounds. To study the possible effect of selected yeast inocula on the fermentation process and subsequent quality of the distillate, a laboratory-scale fermentation of grape marcs was performed. The inoculated yeasts proved to be good colonizers of grape pomace and contributed markedly to rapid sugar consumption, which was completed within 5xa0days. Fermentation products were analysed by gas-chromatography. A time course analysis performed to determine the impact of the inoculated strains on the main aromatic compounds that are concentrated in the product after distillation provided evidence of a positive effect of yeast inoculation.

Engineering Delftia acidovorans DSM39 to produce polyhydroxyalkanoates from slaughterhouse waste.

The inexpensive agricultural fatty by-products could be usefully converted to polyhydroxyalkanoates (PHAs) by properly selected and/or developed microbes. Delftia acidovorans DSM39 is a well-known producer of PHAs with high molar fractions of 4-hydroxybutyrate (4HB), but unable to grow on fatty substrates. The aim of this study was to construct a recombinant strain of D. acidovorans DSM39 using fats-containing waste such as udder, lard and tallow, to produce PHAs. The lipC and lipH genes of Pseudomonas stutzeri BT3, proficient lipolytic isolate, were successfully co-expressed into D. acidovorans DSM39 and the resulting recombinant strain displayed high extracellular enzymatic activity on corn oil. The PHAs production from corn oil achieved high levels (26% of cell dry weight, with about 7% of 4HB). Surprisingly, the recombinant strain produced greater values directly from slaughterhouse residues such as udder and lard (43 and 39%, respectively, with almost 7% of 4HB). Moreover, this work proved the ability of the recombinant D. acidovorans strain to produce PHAs with significant percentage of 4HB, without the supplementation of any precursor in the liquid broth. This research paves the way to the efficient one-step conversion of fatty residues into PHAs having valuable properties exploitable in several medical and industrial applications.

Bacterial diversity of a wooded riparian strip soil specifically designed for enhancing the denitrification process

This research is part of a project aimed at verifying the potential of a specifically assessed wooded riparian zone in removing the excess of combined nitrogen from the Zero River so as to reduce nutrient inputs into the Venice Lagoon. Among the specific objectives of the project, there was the determination of change in the composition of the microbial populations of soil of the wooded riparian strip. The composition of the bacterial communities collected at different depths inside and outside the riparian strip was determined by combined approaches involving cultivation (CFU), microscopic approaches (CTC test), and DNA-based techniques (ARDRA and DGGE). The size of the living population was the same inside and outside the experimental strip, with a minor percentage of culturable bacteria. Higher numbers of metabolically active bacteria and higher bacterial diversity were detected in the internal soil, with deeper soil layers showing reduced diversity, thus indicating that soil management within the riparian strip effectively supports the viability of bacterial communities. Total operational taxonomic units (OTUs) and percentage of single OTUs were also found to be always higher in the internal soil samples for all soil layers, with the percentage of Firmicutes increasing and Actinobacteria decreasing with depth. The increasing soil organic carbon inputs due to the contribution of the growing plants were found to support bacterial diversity in all soil layers. DNA-based analysis also indicated a clear effect of the applied treatments on soil bacterial diversity and a well-defined separation of the bacterial communities related to the different soil layers of the riparian strip.

Efficient computation of nonlinear filter networks with delay-free loops and applications to physically-based sound models

The paper presents a general procedure for the computation of filter networks made of linear filters and nonlinear non-algebraic (dynamic) elements. The method is developed in the Kirchhoff domain and applies to cases where the network contains an arbitrary number of delay-free paths that involve nonlinear elements. Compared to existing techniques the method does not require a rearrangement of the network structure, instead it subdivides the network into computational substructures specified by appropriate matrices related to the network topology. Sufficient conditions are discussed for the applicability of the method, and results are provided that relate performance of the method to the properties of the nonlinear elements and to the network topology. The last part of the paper discusses applications of the method to the simulation of acoustic systems, including multidimensional wave propagation by means of waveguide-mesh techniques.

Outlining a selection procedure for Saccharomyces cerevisiae isolated from grape marc to improve fermentation process and distillate quality.

Nowadays grape marc represents one of the main by-product of winemaking. Many South Europe countries valorize this ligno-cellulosic waste through fermentation and distillation for industrial alcoholic beverage production. The storage of marcs is a crucial phase in the distillation process, due to the physicochemical transformations ascribed to microbial activity. Among the methods adopted by distillers to improve the quality of spirits, the use of selected yeasts has not been explored so far, therefore in this work we evaluated the selection criteria of Saccharomyces cerevisiae strains for grape marc fermentation. The proposed selection procedure included three steps: characterization of phenotypical traits, evaluation of selected strains on pasteurised grape marc at lab-scale (100 g) and pilot-scale fermentation (350 kg). This selection process was applied on 104 strains isolated from grape marcs of different origins and technological treatment. Among physiological traits, β-glucosidase activity level as quality trait seems to be only partially involved in increasing varietal flavour. More effective in describing yeast impact on distillate quality is the ratio higher alcohols/esters that indicates strain ability to increase positive flavours. Finally, evaluating grape marc as source of selected yeasts, industrial treatment rather than varietal origin seems to shape strain technological and quality traits.

Production of Polyhydroxyalkanoates from Fatty Wastes

The production of polyesters from triglyceride containing substrates was investigated. A first filter step based on lipase activity was followed and those bacteria potentially able to degrade oils or animal fats were further tested for their polymer accumulation properties, selected and kept for further studies. In a second step, bacteria were directly grown on animal fats and/or vegetable oils, and polyhydroxyalkanoates (PHAs) accumulation was verified under appropriate incubation conditions. Each substrate, whether of animal or vegetable derivation, supported the growth of a number of the newly isolated strains and among those, some strains were also found to produce reasonably high amounts of PHA. The repeat-unit composition of the polyesters was determined by gas chromatography (GC) analysis of the ß-hydroxyalkanoate methyl esters from the hydrolyzed polymer and some class of co-polymers were also detected. These properties, coupled with the ability of some of the selected isolates to grow and produce lipases on a minimal medium, could be considered as promising in view of possible industrial applications. The overall results indicate that PHAs could be produced from waste containing considerable amounts of fat, oil and grease (FOG), that generally need to be treated for their disposal.

Poly(hydroxyalkanoate) Production by Cupriavidus necator from Fatty Waste Can Be Enhanced by phaZ1 Inactivation

Although PHAs are regarded as an effective substitute for conventional plastics for a number of medical and agricultural applications1 and food packaging2, their full-scale manufacturing is hampered by high production costs3. Factors affecting the cost of PHAs include raw materials availability, suitable process design, and downstream processing4,5. Since almost 50 % of the total production costs can be attributed to the carbon source for microbial growth and polymer production, the selection of renewable, cheap carbon feedstock, specially generated from industrial or agricultural by-products, can provide a way to reduce the price6,7,8. To that end, different industrial by-products, such as whey9,10, molasses11, starch, and waste oils and glycerol, have been investigated as start materials for PHA production12,13,14,15. In this perspective, fatty residues from slaughterhouse represent a promising raw material. For Europe, the amount of animal lipids, also causing expensive disposal problems, is estimated a half a million tons per year16. However, PHA production from waste oils or fats requires microorganisms that should be both excellent PHA producers as well as equipped with enzymatic activities allowing hydrolysation of triglycerides. Cupriavidus necator (formerly Ralstonia eutropha) is one of the best known bacteria among PHA-producing microorganisms15,17. The production of different kinds of PHAs by C. necator using several inexpensive feedstock, including glycerol, has been recently reported18,19,20,21,22, indicating that some strains of this bacterial species could be used for the conversion of fatty residues into PHA. As an alternative, the use of costly commercial enzymes or genetic modification of microorganisms exhibiting high PHA product yields would be required23. In the case of C. necator, its lipase activities could most likely be improved by physiological/technological studies in terms of biomass production and PHA content, but the help of commercial enzymes may still be necessary. A possible strategy to help increase the final PHA yield in a bacterial strain already possessing both high polymer production ability and acceptable triglyceride hydrolytic activity, could originate from the relevant findings regarding C. necator PHA metabolism, physiology, Poly(hydroxyalkanoate) Production by Cupriavidus necator from Fatty Waste Can Be Enhanced by phaZ1 Inactivation