OPTIMISATION OF MICROWAVE PRETREATMENT CONDITIONS OF ORANGE AND PLANTAIN PEELS FOR POLYGALACTURONASE PRODUCTION BY ASPERGILLUS AWAMORI CICC 2040

This study investigated the optimisation of microwave pretreatment of orange and plantain peels for polygalacturonase (PG) production, by Aspergillus awamori CICC 2040, using response surface methodology. The microwave pretreatment factors interacted were particle size (PS) (<0.4250, 0.4250<PS<0.8025, and 0.8025<PS<1.1800 mm), microwave power (240, 480 and 720 W) and time (2.50, 6.25, and 10.00 min.). These factors were interacted to determine combinations for maximum polygalacturonase activity (MPA). Pretreated orange and plantain peel powders were inoculated with 106 spores/mL Aspergillus awamori CICC 2040, incubated at 28oC for 5 days, and crude polygalacturonase was extracted and its activity determined. Same microwave pretreatment combination, 0.8025<PS<1.1800 mm, 720 W and 10.00 min, gave MPA for orange and plantain peels. The MPA from orange and plantain peels was 26.21 and 26.72 U/mL, respectively. F and p values obtained for orange peel powder were 35.42 and 0.00, respectively while those obtained for plantain peel powder were 5.71 and 0.006, respectively. R2 and R2 (adjusted) of 96.96 and 94.22%, respectively were obtained for PG activity produced using orange peel powder while 90.71 and 79.04% were recorded for PG activity produced using plantain peel powder. Optimised microwave pretreatment conditions of orange and plantain peels for MPA from Aspergillus awamori CICC 2040 were established. Keywords: Aspergillus awamori, Fruit peel, Microwave, Optimisation, Polygalacturonase, Pretreatment,

Optimisation of alkaline pretreatment conditions of orange and plantain peels for polygalacturonase production by Aspergillus awamori CICC 2040

This study investigated the optimisation of alkaline pretreatment of orange and plantain peels for polygalacturonase (PG) production by Aspergillus awamori CICC 2040 using response surface methodology. The factors evaluated were particle size, PS (< 0.4250, 0.4250 < PS < 0.8025 and 0.8025 < PS < 1.1800 mm), NaOH molarity (0.010, 0.055, and 0.100 M), and time (1.0, 6.5, and 12.0 h). These factors were interacted to determine the most suitable combinations for maximum polygalacturonase activity (MPA). The pretreated orange and plantain peel powders were inoculated with 106 spores/mL Aspergillus awamori CICC 2040 was incubated at 28 oC for 5 days, and crude PG was extracted and its activity determined. The alkaline pretreatment combinations that gave MPA were <0.4250 mm, 0.100 M, and 1.0 h, and 0.8025 < PS < 1.1800 mm, 0.010 M, and 1.0 h for orange and plantain peel powders, respectively. The MPA obtained from the pretreated orange and plantain peel powders were 38.46 and 38.82 U/mL, respectively. Optimised alkaline pretreatment conditions of the orange and plantain peels for MPA, produced by Aspergillus awamori CICC 2040, were established. Keywords: Aspergillus awamori CICC 2040, Peel, Optimisation, Polygalacturonase, Pretreatment

Effect of low temperature culture on the biological characteristics and aggressiveness of Sclerotinia sclerotiorum and Sclerotinia minor

Sunflower White Mold caused by Sclerotinia sclerotiorum and Sclerotinia minor is a devastating disease worldwide. To investigate the effect of low temperature (4 °C) on biological characteristics and aggressiveness of isolates of the two species, which were collected from the same field in Baiyinchagan, Inner Mongolia, their mycelial growth rate, oxalic acid secretion level and polygalacturonase activity were compared under normal culture temperature (23 °C) and low temperature (4 °C). Aggressiveness was also evaluated on detached leaves by inoculating the isolates produced in both temperatures. The results suggested that culture of isolates at 4 °C not only promoted mycelial growth, but also enhanced secretion of oxalic acid and polygalacturonase activity of both S. sclerotiorum and S. minor isolates compared to that cultured at 23 °C. Additionally, the corresponding aggressiveness of tested isolates of the two species also increased after culture at 4 °C. However, S. sclerotiorum always showed faster mycelial growth, higher oxalic acid levels and greater polygalacturonase activity than S. minor at both 23 °C and 4 °C, indicating that S. sclerotiorum is generally the more aggressive species than S. minor.

Sclerotinia sclerotiorum KK-1 isolate from Belarus: pathogenicity factors and glyphosate sensitivity

In the presence work, mycelial growth, sclerotia formation, polygalacturonase, a-amylase and cellulase activities of a Belarusian fungal isolate Sclerotinia sclerotiorum KK-1 collected from infected сarrot (Daucus carota subsp. sativus) were analyzed. It was established that polygalacturonase was induced by pectin and subject to catabolite repression by glucose. The ability of the isolate to produce oxalic acid, an important factor of pathogenesis, was observed throughout fungus incubation on PDA medium amended with bromophenol blue. Glyphosate (commercial counterpart «Tornado») starting from its level in the medium of 200 mg/L caused a significant inhibition of mycelial growth and sclerotia formation. It was observed that a-amylase and cellulase activities were inhibited by glyphosate unlike polygalacturonase activity.

Effect of pre-harvest calcium silicate on post-harvest quality of tomatoes

The present work evaluated the influence of calcium silicate on the polygalacturonase enzyme activity, respiration, ethylene, and the physicochemical characteristics on the post-harvest quality of two tomato hybrids. The experimental design was of randomized blocks, with four repetitions in protected cultivation environment. The treatments were distributed in a 2 x 5 factorial scheme, corresponding to the hybrids (Ivety and Natalia) and five doses of calcium silicate (0, 150, 300, 450 and 600 kg ha-1), which were applied on the same day as the pots were filled. Evaluations were carried out on the fruits, namely: ethylene production, fruit respiration, firmness, number of loculus, polygalacturonase activity, total carotenoids, lycopene, phenolic compounds, soluble solids content, pH, titratable acidity and ascorbic acid content. The application of calcium silicate provided the reduction of ethylene production and fruit respiration. Natalia hybrid showed low polygalacturonase activity, this difference being due to genetic variabilityThe increase of calcium silicate doses provided the reduction of polygalacturonase enzyme concentration due to its constitution in the cell wall. The concentrations of lycopene, phenolic compounds, soluble solids, pH, titratable acidity and ascorbic acid in the fruits increased in response to the increasing doses of calcium silicate for 'Ivety'. Hybrids present distinct behaviors on the influence of the fertilization of tomatoes with calcium silicate, which can increase the post-harvest conservation and improve the physical-chemical characteristics of tomato fruits.

New Arctic Bacterial Isolates with Relevant Enzymatic Potential

Fragments of wood drifting in the vicinity of Spitzbergen were used for the isolation of microorganisms, carried out using atypical carbon sources: colloidal chitin, cellulose and carboxymethylcellulose, xylan, casein, tributrin and olive oil. Purified cultures were subjected to a three-step identification: with classical methods, using MALDI-TOF MS Biotyper whole-cell protein fingerprinting, and molecular analysis of 16S rDNA. Subsequently, a preliminary assessment of the enzymatic potential of isolates was carried out. As a result, cellulolytic activity was observed in more than 50% of the bacterial strains, exhibiting activity of 0.30–0.40 U/mL. Over 53% of the isolates demonstrated xylanolytic activity, of which the highest reached from 0.40 to 0.90 U. Polygalacturonase activity of 0.003–1.6 was also demonstrated in half of the bacterial strains studied. Proteolytic activity of isolates did not exceed 0.3 U. An important highlight was the ability of fluorescent dye production by certain strains, grown on skim milk-agar, but also on pure meat extract.

Synthesis and potential application of polygalacturonase from a Penicillium brasilianum isolate

The aim of this study was to evaluate the synthesis of pectinase from Penicillium brasilianum in shake flasks and address their potential for industrial applications. A Plackett-Burman design followed by a complete second order design were used for the screening of most important factors and to maximize the polygalacturonase activity, respectively. Maximum polygalacturonase activity was 52.8 U mL-1 at 48 hours of bioproduction. The kinetic evaluation for substrate consumption showed that 42% total organic carbon, 52 nitrogen, 23 magnesium, and 60% potassium were consumed. The crude enzyme complex was used on commercial mango juice clarification, and, at a 0.5% concentration (v v-1) reduced viscosity by 10%, turbidity by 12% and clarification by 23%. Therefore, the results presented in this study could provide valuable and beneficial information for the food and enzyme industries (juice) as well as being a new landmark to microbiology by providing essential knowledge on P. brasilianum growing needs.