Stefania Costa

Optimized Production of Xylitol from Xylose Using a Hyper-Acidophilic Candida tropicalis

The yeast Candida tropicalis DSM 7524 produces xylitol, a natural, low-calorie sweetener, by fermentation of xylose. In order to increase xylitol production rate during the submerged fermentation process, some parameters-substrate (xylose) concentration, pH, aeration rate, temperature and fermentation strategy-have been optimized. The maximum xylitol yield reached at 60–80 g/L initial xylose concentration, pH 5.5 at 37 °C was 83.66% (w/w) on consumed xylose in microaerophilic conditions (kLa = 2·h−1). Scaling up on 3 L fermenter, with a fed-batch strategy, the best xylitol yield was 86.84% (w/w), against a 90% of theoretical yield. The hyper-acidophilic behaviour of C. tropicalis makes this strain particularly promising for industrial application, due to the possibility to work in non-sterile conditions.

Quantification of Lycopene, β-Carotene, and Total Soluble Solids in Intact Red-Flesh Watermelon (Citrullus lanatus) Using On-Line Near-Infrared Spectroscopy

A great interest has recently been focused on lycopene and β-carotene, because of their antioxidant action in the organism. Red-flesh watermelon is one of the main sources of lycopene as the most abundant carotenoid. The use of near-infrared spectroscopy (NIRS) in post-harvesting has permitted us to rapidly quantify lycopene, β-carotene, and total soluble solids (TSS) on single intact fruits. Watermelons, harvested in 2013–2015, were submitted to near-infrared (NIR) radiation while being transported along a conveyor belt system, stationary and in movement, and at different positions on the belt. Eight hundred spectra from 100 samples were collected as calibration set in the 900–1700 nm interval. Calibration models were performed using partial least squares (PLS) regression on pre-treated spectra (derivatives and SNV) in the ranges 2.65–151.75 mg/kg (lycopene), 0.19–9.39 mg/kg (β-carotene), and 5.3%–13.7% (TSS). External validation was carried out with 35 new samples and on 35 spectra. The PLS models for intact watermelon could predict lycopene with R2 = 0.877 and SECV = 15.68 mg/kg, β-carotene with R2 = 0.822 and SECV = 0.81 mg/kg, and TSS with R2 = 0.836 and SECV = 0.8%. External validation has confirmed predictive ability with R2 = 0.805 and RMSEP = 16.19 mg/kg for lycopene, R2 = 0.737 and RMSEP = 0.96 mg/kg for β-carotene, and R2 = 0.707 and RMSEP = 1.4% for TSS. The results allow for the market valorization of fruits.

Effects of Moisture and Particle Size on Quantitative Determination of Total Organic Carbon (TOC) in Soils Using Near-Infrared Spectroscopy

Near-Infrared Spectroscopy is a cost-effective and environmentally friendly technique that could represent an alternative to conventional soil analysis methods, including total organic carbon (TOC). Soil fertility and quality are usually measured by traditional methods that involve the use of hazardous and strong chemicals. The effects of physical soil characteristics, such as moisture content and particle size, on spectral signals could be of great interest in order to understand and optimize prediction capability and set up a robust and reliable calibration model, with the future perspective of being applied in the field. Spectra of 46 soil samples were collected. Soil samples were divided into three data sets: unprocessed, only dried and dried, ground and sieved, in order to evaluate the effects of moisture and particle size on spectral signals. Both separate and combined normalization methods including standard normal variate (SNV), multiplicative scatter correction (MSC) and normalization by closure (NCL), as well as smoothing using first and second derivatives (DV1 and DV2), were applied to a total of seven cases. Pretreatments for model optimization were designed and compared for each data set. The best combination of pretreatments was achieved by applying SNV and DV2 on partial least squares (PLS) modelling. There were no significant differences between the predictions using the three different data sets (p < 0.05). Finally, a unique database including all three data sets was built to include all the sources of sample variability that were tested and used for final prediction. External validation of TOC was carried out on 16 unknown soil samples to evaluate the predictive ability of the final combined calibration model. Hence, we demonstrate that sample preprocessing has minor influence on the quality of near infrared spectroscopy (NIR) predictions, laying the ground for a direct and fast in situ application of the method. Data can be acquired outside the laboratory since the method is simple and does not need more than a simple band ratio of the spectra.

Quantitative Determination of Fluorine Content in Blends of Polylactide (PLA)–Talc Using Near Infrared Spectroscopy

Near-infrared spectroscopy (NIRS) has been widely used for quantitative and/or qualitative determination of a wide range of matrices. The objective of this study was to develop a NIRS method for the quantitative determination of fluorine content in polylactide (PLA)-talc blends. A blending profile was obtained by mixing different amounts of PLA granules and talc powder. The calibration model was built correlating wet chemical data (alkali digestion method) and NIR spectra. Using FT (Fourier Transform)-NIR technique, a Partial Least Squares (PLS) regression model was set-up, in a concentration interval of 0 ppm of pure PLA to 800 ppm of pure talc. Fluorine content prediction (R2cal = 0.9498; standard error of calibration, SEC = 34.77; standard error of cross-validation, SECV = 46.94) was then externally validated by means of a further 15 independent samples (R2EX.V = 0.8955; root mean standard error of prediction, RMSEP = 61.08). A positive relationship between an inorganic component as fluorine and NIR signal has been evidenced, and used to obtain quantitative analytical information from the spectra.

Synthesis of Hydroxy-Androstane-1,4-Diene-3, 17-Dione Derivatives by Biotransformations of Bile Acids with Pseudomonas alcaliphila

The synthesis of hydroxy-androstane-1,4-diene-3,17-dione derivatives (2a-d) by biotransformations with Pseudomonas alcaliphila of bile acids (1a-d) was reported. The scale-up of addition of deoxycholic acid (1a), cholic acid (1b), and chenodeoxycholic acid (1c) (1 g/L until 10 g/L) to the culture broth of P. alcaliphila switches the degradation process to the synthesis of 12β-hydroxy-androstane-1,4-diene-3,17-dione (2a, 95%), 7α,12β-dihydroxy-androstane- 1,4-diene-3,17-dione (2b, 52%), and 7α-hydroxy-androstane-1,4-diene-3,17-dione (2c, 23%) Also hyodeoxycholic acid (1d) was transformed by P. alcaliphila to 6α-hydroxy-androstane-1,4-diene-3,17-dione (2d) with as much good yields (83%) but with lower concentration (1 g/L) in the culture broth.

Biocatalytic Activity of Fresh Passiflora Spp. Leaves in EnantioselectiveOxido-Reduction

The biocatalytic activity of five species of Passiflora leaves (i.e. P. amethyst, P. incarnata, P. quadrangularis, P. edulis, P. cerulea) was tested in the reduction of the ketone “cocktail” (i.e. 5-hexen-2-one 1, acetophenone 2, cisbicyclo[ 3.2.0]hept-2-en-6-one 3 and 2-methylcyclohexanone 4) and in the oxidation of the corresponding alcohols “cocktail” (i.e. 5-hexen-2-ol 5, 1-phenylethanol 6, endo-bicyclo[3.2.0]hept-2-en-6-ol 7, exo-bicyclo[3.2.0] hept-2-en- 6-ol 8, trans-2-methylcyclohexanol 9 and cis-2-methylcyclohexanol 10). P. amethyst and P. incarnata show the best activity in the reduction, while P. quadrangularis affords low yield in reduction but gives appreciable results in oxidation towards a cocktail of model substrates. This simple screening permits to test the potential of parts of fresh plants that can be used as biocatalysts in more ecologically and economically promising transformations.

Potential of Near Infrared Spectroscopy for Classification of Different Delignificant Pre-Treatments on Banana Rachis

Delignificant pretreatments are fundamental in lignocellulosic materials preprocessing to remove lignin from biomass. Current wet chemical methods are time-consuming, labor-intensive and use hazardous reagents. Near Infrared Spectroscopy (NIRS) provides rapid and non-destructive analysis, and has shown promising results. Spectra collection (8000-4000 cm-1), combined with chemometric analysis based on Cluster Analysis and Principal Component Analysis, has allowed to perform qualitative study of banana rachis, a lignocellulosic residue of agricultural production.

Biotransformations of Bile Acids with Bacteria from Cayambe Slaughterhouse (Ecuador): Synthesis of Bendigoles

The biotransformations of cholic acid (1a), deoxycholic acid (1b), and hyodeoxycholic acid (1c) to bendigoles and other metabolites with bacteria isolated from the rural slaughterhouse of Cayambe (Pichincha Province, Ecuador) were reported. The more active strains were characterized, and belong to the genera Pseudomonas and Rhodococcus. Various biotransformation products were obtained depending on bacteria and substrates. Cholic acid (1a) afforded the 3‐oxo and 3‐oxo‐4‐ene derivatives 2a and 3a (45% and 45%, resp.) with P. mendocina ECS10, 3,12‐dioxo‐4‐ene derivative 4a (60%) with Rh. erythropolis ECS25, and 9,10‐secosteroid 6 (15%) with Rh. erythropolis ECS12. Bendigole F (5a) was obtained in 20% with P. fragi ECS22. Deoxycholic acid (1b) gave 3‐oxo derivative 2b with P. prosekii ECS1 and Rh. erythropolis ECS25 (20% and 61%, resp.), while 3‐oxo‐4‐ene derivative 3b was obtained with P. prosekii ECS1 and P. mendocina ECS10 (22% and 95%, resp.). Moreover, P. fragi ECS9 afforded bendigole A (8b; 80%). Finally, P. mendocina ECS10 biotransformed hyodeoxycholic acid (1c) to 3‐oxo derivative 2c (50%) and Rh. erythropolis ECS12 to 6α‐hydroxy‐3‐oxo‐23,24‐dinor‐5β‐cholan‐22‐oic acid (9c, 66%). Bendigole G (5c; 13%) with P. prosekii ECS1 and bendigole H (8c) with P. prosekii ECS1 and Rh. erythropolis ECS12 (20% and 16%, resp.) were obtained.

Valorization of Tomato Dried Peels Powder as Thickening Agent in Tomato Purees

Tomato pomade, consisting of peels and seeds, represents 3-4% of fresh fruit weight. If it remains a waste, it gives rise to disposal problems and aggravate environmental pollution. Our aim was to evaluate the potential of dried peels powder as thickening ingredient in commercial tomato purees. Dried peels were ground in fine and rough sizes and physic-chemically characterized. Samples of creamy and rustic purees with tomato fine and rough dried peels powders at different percentages (0.5-5.0%) were prepared and tested for rheological properties and organoleptic characteristics (colour and flavour). The addiction of 3.0% of fine and 1.0% of rough dried peels powder to rustic purees, and 2.0% of fine dried peels powder to creamy purees resulted as the best combination to reduce the impact of industrial evaporation. The proposed approach could transform a waste in a value-added product to be reused, even in the producer’s supply chain itself.