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Iron is a fundamental element for plants as well as for microorganisms and several pathogens, including Rhizoctonia solani, one of the main soil-borne pathogens of tomato. This study demonstrated the ability of Aureobasidium pullulans strain L1 to produce siderophores and how these molecules were, directly and indirectly, connected to its antagonistic activity and iron bioavailability. By ICP-OES (Inductively Coupled Plasma - Optical Emission Spectroscopy) trace analysis, the strain displayed the ability to increase the bioavailability of Fe (II) in the soil by almost 50% 30 days after inoculation. Also, the bioavailability of Mn, Cu, and Zn was increased after 30 days of incubation in the soil by 31.8%, 38.4%, and 27.1%, respectively. In in vivo assays, A. pullulans L1 strain showed a growth promotion of tomato roots length and stem diameter, respectively by 19.1% and 27.3%, and acted as a biocontrol agent (BCA) against R. solani (80% of inhibition). The results demonstrate a new aspect of this microorganism, usually applied as an antagonist of postharvest fruit diseases, to explore in different environments and against different pathogens, such as soil-borne pathogens.

Agricultural land abandonment is an emerging problem in European Union (EU), and about 11% of agricultural EU land is at high risk of abandonment in the coming 10 years. Land abandonment may have both positive and negative effects in ecosystems. Due to the potential for land abandonment to increase soil fertility, the study of vegetation succession effects on soil quality is of great importance. In this study, we investigated an abandoned vineyard where, after a period of 30 years, rows and alleys were characterized by two different forms of vegetation succession: natural recolonization by trees along the rows and by herbaceous vegetation in the alleys. No-tilled alleys covered by herbaceous vegetation of a neighboring conventionally cultivated vineyard were used as a comparison. Soil samples were chemically characterized (pH, extractable element, and available and total metals), and analyzed for the determination of carbon (C) and nitrogen (N) pools, hydrolytic and phenol oxidizing (PO) enzyme activities involved in C, N, and phosphorus (P) cycles, and the enzyme ratios. Results highlighted that natural recolonization by trees increased the organic C and N soil pools by 58% and 34%, respectively, compared to the natural recolonization by herbaceous vegetation. Moreover, natural recolonization by trees reduced β-glucosidase by 79%, urease by 100%, alkaline phosphastase by 98%, acid phosphatase specific hydrolytic activities by 50%, and catechol oxidase and laccase specific oxidative activities by 127% and 119%, respectively, compared to the renaturalization by herbaceous vegetation. In addition, the natural recolonization by trees reduced the C (βglu):C (PO) enzymes ratio by 16% compared to that of the conventional vineyard. Comparing the natural recolonization by herbaceous vegetation with that of the conventional vineyard revealed little significant difference (15% of the measured and calculated parameters), in particular, PO activities significantly decreased in the renaturalized vineyard with herbaceous vegetation by 49% (catechol oxidase) and 52% (laccase), and the C (βglu):C (PO) enzyme ratio showed a reduction (−11%) in the vineyard naturally recolonized by herbaceous vegetation compared to the conventional vineyard. This highlights that the type of vegetation succession that takes place after land abandonment may have a significant impact in terms of soil fertility and C accrual potential. These results help to focus attention on the practices used in agro-forestry that should be adopted in abandoned agro-ecosystems to increase their biodiversity, soil C stock, and soil quality, because these indicators are affected by the type of vegetative coverage.

Protein hydrolyzates (PHs) are a well-known group of plant biostimulants that are obtained by thermal, chemical, enzymatic or mixed hydrolysis from animal or plant sources. PHs are mainly applied to plants with the aim to improve their nutrition level, stimulate metabolism, and increase resistance to abiotic stress. Chemically, the PHs are a mixture of free amino acids, oligo- and polypeptides. Considering the differences in the source materials and hydrolytic processes used for their production it is not surprising that PHs are a very complex and inhomogeneous category of biostimulants. This is a critical point that should be considered by both manufacturers and potential users of such products. With the aim to identify a putative correlation among PHs physic-chemical properties, the different source materials and the hydrolytic process used for their production, 22 PHs available on the market were analyzed for: (i) total amino acids concentration, (ii) free amino acids concentration, (iii) degree of racemization, (iv) degree of hydrolysis and (v) apparent average molecular size. The obtained results confirmed the inhomogeneity PHs. However, the chosen parameters were able to provide information about the above-mentioned correlation. Total amino acids in particular were useful for the identification of the original source material. The degree of racemization was useful for the identification of the type of hydrolysis used during production (chemical or enzymatic). The degree of hydrolysis and free amino acid concentrations were useful for the identification of the intensity of the hydrolytic process. The average molecular size was useful for the identification of polydispersity of the peptide size. In conclusion, the PHs can be adequately characterized only through a multi-analytical approach.

Vanillin (4-hydroxy-3-methoxybenzaldehyde), the major component of natural vanilla, is widely used in food, beverage, cosmetic and pharmaceutical industries. Since natural vanillin, extracted from the pods of the tropical vanilla orchid, features both high price and limited supply, chemically synthesized vanillin occupies more than 99% of the market share. The increasing concern for health and nutrition stimulates a worldwide demand for “natural” vanillin. Our studies have been focused on vanillin production from ferulic acid by using a Pseudomonas sp. strain and from capsaicin via an enzymatic process. In both microbial and enzymatic transformations the productivity can be potentially enhanced by in-situ removal of vanillin, avoiding the product inhibition and further transformation of vanillin to side products. The goal of this research is to evaluate the potential of using membrane based solvent extraction for the recovery of vanillin in view of the on-line extraction from the bioconversion broth, thus coupling bioconversion and separation. Various solvents were tested measuring the partition coefficients for vanillin and other relevant compounds. Good properties were shown by ethyl and n-butyl acetate, which allow the selective removal of the produced vanillin from the bioconversion broth removing only a minor extend of the substrates. The partition coefficient of vanillin depends on pH: at higher pH values vanillin becomes more soluble in water than in the solvent. This behaviour suggests the possibility to counter-extract vanillin from the vanillin rich solvent phase by using alkaline water, from which pure vanillin can be eventually obtained by crystallization. Extraction and counter-extraction experiments were performed by hollow fibre modules; the feed flowed either through the lumen or in the shell side. The kinetics of mass transfer was investigated in batch experiments. The overall mass transfer coefficients were calculated from the data and compared with theoretical values.

BACKGROUND: Wheat bran contains a large amount of ferulic acid, which can be released through enzymatic hydrolysis and bioconverted into vanillin. A previous study has shown that ferulic acid purification from bran carbohydrates with the Amberlite IRA 95 resin allowed an increased vanillin molar yield. In this work, alternative ferulic acid recovery methods were proposed and the possibility of exploiting the residual carbohydrate-rich water phase was explored. RESULTS: Ferulic acid was recovered from crude wheat bran hydrolyzate by: (i) a hydrophobic sorbent cartridge (ISOLUTE ENV+): (ii) ethyl acetate extraction; and (iii) the resin previously employed. The highest recovery percentage (95%) was obtained with ISOLUTE ENV+, which also allowed an interesting vanillin molar yield from ferulic acid bioconversion (75% from 0.5 mmol L−1 ferulic acid). The residual water phase was a good growth substrate for the microorganism operating the bioconversion. Cells grown on thismatrix could efficiently bioconvert the recovered ferulic acid to vanillin CONCLUSION: The possibility of efficiently recovering ferulic acid from wheat bran hydrolyzates, bioconverting it into vanillin, and valorizing the sugar-rich exhausted water fraction was demonstrated in this work. The approach allowed the production of a value-added fine-chemical from a food-industry by-product. c 2009 Society of Chemical Industry