The waste materials from the carob processing industry are a potential resource for second-generation bioethanol production. These by-products are small carob kibbles with a high content of soluble sugars (45-50%). Batch and fed-batch Saccharomyces cerevisiae fermentations of high density sugar from carob pods were analyzed in terms of the kinetics of sugars consumption and ethanol inhibition. In all the batch runs, 90-95% of the total sugar was consumed and transformed into ethanol with a yield close to the theoretical maximum (0.47-0.50 g/g), and a final ethanol concentration of 100-110 g/l. In fed-batch runs, fresh carob extract was added when glucose had been consumed. This addition and the subsequent decrease of ethanol concentrations by dilution increased the final ethanol production up to 130 g/l. It seems that invertase activity and yeast tolerance to ethanol are the main factors to be controlled in carob fermentations. The efficiency of highly concentrated carob fermentation makes it a very promising process for use in a second-generation ethanol biorefinery.

Centaurea calcitrapa suspension cultures were grown either in Erlenmeyer flasks or in a mechanically stirred bioreactor. Its rheological behaviour, when fitted to the Oswald-de Waele model (power law), showed pseudoplastic characteristics in both cases. The flow behaviour index (n) decreased over the course of a growth cycle and the consistency index (K) increased, reached a value of 1.81 N sn m(-2 )run on 2 l bioreactor. Bioreactor cultivation of C. calcitrapa cells at different agitation rates (30, 60, 100 and 250 rpm), highlighted the influence of shear forces on cell viability loss (90-34%) and phenol accumulation (74-140 microg l(-1)), due to increased stirring speeds. Analysis of these results suggests that this cell line is shear-sensitive. An empirical exponential correlation was defined between apparent viscosity and biomass concentration, under the studied conditions, giving the possibility to estimate the prevailing broth regime and to optimize bioreactor design.

Large-scale production has been the major obstacle to the success of many biopesticides. The spreading of microbial biocontrol agents against postharvest disease, as a safe and environmentally friendly alternative to synthetic fungicides, is quite dependent on their industrial mass production from low-cost raw materials. Considerable interest has been shown in using agricultural waste products and by-products from food industry as nitrogen and carbon sources. In this work, carob pulp aqueous extracts were used as carbon source in the production of the biocontrol agent Pantoea agglomerans PBC-1. Optimal sugar extraction was achieved at a solid/liquid ratio of 1:10 (w/v), at 25°C, for 1 h. Batch experiments were performed in shake flasks, at different concentrations and in stirred reactors at two initial inoculums concentrations, 10(6) and 10(7) cfu ml(-1). The initial sugar concentration of 5 g l(-1) allowed rapid growth (0.16 h(-1)) and high biomass productivity (0.28 g l(-1) h(-1)) and was chosen as the value for use in stirred reactor experiments. After 22 and 32 h of fermentation the viable population reached was 3.2 × 10(9) and 6.2 × 10(9) cfu ml(-1) in the fermenter inoculated at 10(6) cfu ml(-1) and 2.7 × 10(9) and 6.7 × 10(9) cfu ml(-1) in the bioreactor inoculated at 10(7) cfu ml(-1). A 78% reduction of the pathogen incidence was achieved with PBC-1 at 1 × 10(8) cfu ml(-1), grown in medium with carob extracts, on artificially wounded apples stored after 7 days at 25°C against P. expansum.

This paper describes the effect of NaCl on the respiration of Citrus cell suspensions namely on the induction of the alternative oxidase. The exposure of two Citrus (cvs. Carvalhal tangor and Valencia late) cell suspensions to 200 or 400 mM NaCl lead to a reduction on cell respiration rates. Under these conditions, the respiration rate decreased less in the presence of KCN indicating a stimulation of the capacity of the alternative oxidase (AOX). In addition, immunoblots showed an increase on the amount of AOX protein. Antibodies raised against the Sauromatum guttatum enzyme recognized the reduced form of the enzyme near the 35 kDa band. The protein accumulation was correlated with the significantly higher AOX capacity observed for cv. Carvalhal tangor.

Industrial‐scale plant cell based bioprocesses are limited because of technological challenges associated with mass transfer and mixing in the heterogeneous broth, which typically displays non‐Newtonian characteristics. Cultures of Centaurea calcitrapa cells, presenting milk‐clotting activity, were established in a 7‐L stirred‐tank reactor (STR), keeping the initial mass transfer conditions constant, to gain a better understanding of the effects of the hydrodynamic environment and mass transfer on protease production. Cell suspensions grown in an STR equipped with one single marine propeller or two Rushton turbines showed the highest protease activities and biomass production, corresponding to the adequate mass transfer achieved under the tested bioreactor conditions. The key factors improving milk‐clotting protease production in a bioreactor were an efficient mass transfer and good bulk mixing without the formation of stagnant zones, while a compromise had to be established in relation to the hydrodynamic shear conditions.