When grown in the appropriate medium, several yeast species produce pectinases able to degrade pectic substances. It is mainly exocellular endopolyga

Agriculture, together with aquaculture, supplies most of the foodstuffs required by the world human population to survive. Hence, bacterial diseases affecting either agricultural crops, fish, or shellfish not only cause large economic losses to producers but can even create food shortages, resulting in malnutrition, or even famine, in vulnerable populations. Years of antibiotic use in the prevention and the treatment of these infections have greatly contributed to the emergence and the proliferation of multidrug-resistant bacteria. This review addresses the urgent need for alternative strategies for the use of antibiotics, focusing on the use of bacteriophages (phages) as biocontrol agents. Phages are viruses that specifically infect bacteria; they are highly host-specific and represent an environmentally-friendly alternative to antibiotics to control and kill pathogenic bacteria. The information evaluated here highlights the effectiveness of phages in the control of numerous major pathogens that affect both agriculture and aquaculture, with special emphasis on scientific and technological aspects still requiring further development to establish phagotherapy as a real universal alternative to antibiotic treatment.

An α-xylosidase active against xyloglucan oligosaccharides was purified from cabbage (Brassica oleracea var. capitata) leaves. Two peptide sequences were obtained from this protein, the N-terminal and an internal one, and these were used to identify an Arabidopsis gene coding for an α-xylosidase that we propose to callAtXYL1. It has been mapped to a region of chromosome I between markers at 100.44 and 107.48 cM. AtXYL1comprised three exons and encoded a peptide that was 915 amino acids long, with a potential signal peptide of 22 amino acids and eight possible N-glycosylation sites. The protein encoded byAtXYL1 showed the signature regions of family 31 glycosyl hydrolases, which comprises not only α-xylosidases, but also α-glucosidases. The α-xylosidase activity is present in apoplastic extractions from Arabidopsis seedlings, as suggested by the deduced signal peptide. The first eight leaves from Arabidopsis plants were harvested to analyze α-xylosidase activity and AtXYL1expression levels. Both increased from older to younger leaves, where xyloglucan turnover is expected to be higher. When this gene was introduced in a suitable expression vector and used to transformSaccharomyces cerevisiae, significantly higher α-xylosidase activity was detected in the yeast cells. α-Glucosidase activity was also increased in the transformed cells, although to a lesser extent. These results show thatAtXYL1 encodes for an apoplastic α-xylosidase active against xyloglucan oligosaccharides that probably also has activity againstp-nitrophenyl-α-d-glucoside.

Saccharomyces cerevisiae CECT1389 secreted an extracellular endopolygalacturonase (EC 3.2.1.15) when grown in shake flasks in medium containing galactose alone, or either galactose and polygalacturonic acid or galactose and galacturonic acid as the carbon sources. The synthesis of the enzyme was repressed by glucose and by high oxygen tensions. The enzyme was partially purified by gel exclusion chromatography over Sephacryl S-200, where it showed an apparent molecular mass of 39 kDa; the value determined by high-performance liquid chromatography (HPLC) was 65 kDa. The optimal temperature and pH for enzyme activity were45 °C and 5.5, respectively. The K_m and V_max values for polygalacturonic acid were 4.7 mg∙mL⁻¹ and 6.4 nmol∙mL⁻¹∙min⁻¹. The K_i for HgCl₂ was 6.8 × 10⁻⁵ M. The enzyme exhibited an endo-splitting mechanism as deduced from viscosimetry experiments as well as from an HPLC study of the end products.Key words: characterization, endopolygalacturonase, Saccharomyces cerevisiae.