Vanillin production from ferulic acid with Pseudomonas fluorescens BF13-1p4

Bioconversion of ferulic acid to vanillin represents an attractive opportunity for replacing synthetic vanillin with a bio-based product, that can be label “natural”, according to current food regulations. Ferulic acid is an abundant phenolic compound in cereals processing by-products, such as wheat bran, where it is linked to the cell wall constituents. In this work, the possibility of producing vanillin from ferulic acid released enzymatically from wheat bran was investigated by using resting cells of Pseudomonas fluorescens strain BF13-1p4 carrying an insertional inactivation of vdh gene and ech and fcs BF13 genes on a low copy number plasmid. Process parameters were optimized both for the biomass production phase and the bioconversion phase using food-grade ferulic acid as substrate and the approach of changing one variable while fixing the others at a certain level followed by the response surface methodology (RSM). Under optimized conditions, vanillin up to 8.46 mM (1.4 g/L) was achieved, whereas highest productivity was 0.53 mmoles vanillin L-1 h-1). Cocktails of a number of commercial enzyme (amylases, xylanases, proteases, feruloyl esterases) combined with bran pre-treatment with steam explosion and instant controlled pressure drop technology were then tested for the release of ferulic acid from wheat bran. The highest ferulic acid release was limited to 15-20 % of the ferulic acid occurring in bran, depending on the treatment conditions. Ferulic acid 1 mM in enzymatic hydrolyzates could be bioconverted into vanillin with molar yield (55.1%) and selectivity (68%) comparable to those obtained with food-grade ferulic acid after purification from reducing sugars with a non polar adsorption resin. Further improvement of ferulic acid recovery from wheat bran is however required to make more attractive the production of natural vanillin from this by-product.

Risposte di resistenza a batteri fitopatogeni di importanti specie coltivate indotte da molecole segnale di diversa natura

A modern management of crop protection should be based on integrated control programmes, including the use of environmentally safe products. Antagonistic/beneficial bacteria and resistance inducers may have a great potential in the prophylaxis of diseases caused by common and quarantine pathogens. This work was carried out to confirm the ability of the known strain IPV-BO G19 (Pseudomonas fluorescens) against fire blight (Erwinia amylovora), as well as to evaluate their efficacy against southern bacterial wilt of tomato (Ralstonia solanacearum) and grapevine crown gall (Agrobacterium vitis). A virulent strain of R. solanacearum race 3 was inhibited by the antagonist on plate. When the pathogen was inoculated 48 h after their application to the root apparatus of tomato plants grown in a climatic chamber, bacterial wilt progression rate was clearly reduced. Moreover the defence response evoked by IPV-BO G19 was studied in tomato plants by monitoring the transcription of genes codifying for three PRs as PR-1a, PR-4, PR-5 and for an intracellular chitinase using multiplex RT-PCR and Real Time RT-PCR. In two field trials during 2005 and 2006, the strain IPV-BO G19 was compared with biofungicides and some abiotic elicitors to protect actively growing shoots of pear scions against fire blight. In both trials, IPV-BO G19 plus Na-alginate gave a high level of protection, three weeks after wound inoculation with E. amylovora. In pear leaf tissues treated with the antagonistic strain IPV-BO G19, catalase, superoxyde dismutase and peroxidise activity was evaluated as markers of induced resistance. The IPV-BO G19 strain was compared with other bioagents and resistance inducers to prevent grapevine crown gall under glasshouse and vineyard conditions.