Production, partial purification and characterization of α-l-rhamnosidase from Penicillium ulaiense

Abstract

Penicillium ulaiense is a post-harvest pathogenic fungus that attacks citrus fruits. The objective of this work was to study this microorganism as an a-L-rhamnosidase producer and to characterize it from P. ulaiense. The enzyme under study is used for different applications in food and beverage industries. a-L-Rhamnosidase was produced in a stirred-batch reactor using rhamnose as the main carbon source. The kinetic parameters for the growth of the fungi and for the enzyme production were calculated from the experimental values. A method for partial purification, including (NH 4 ) 2 SO 4 precipitation, incubation at pH 12 and DEAE-sepharose chromatography yielded an enzyme with very low b-glucosidase activity. The pH and temperature optima were 5.0 and 60°C, respectively. The Michaelis-Menten constants for the hydrolysis of p-nitrophenyl-a-L-rhamnoside were V max = 26 ± 4 IU ml -1 and K m = 11 ± 2 mM. The enzyme showed good thermostability up to 60°C and good operational stability in white wine. Co 2? affected positively the activity; EDTA, Mn 2? , Mg 2? , dithiotreitol and Cu 2? reduced the activity by different amounts, and Hg 2? completely inhibited the enzyme. The enzyme showed more activity on p-nitrophenyl-a-L-rhamnoside than on naringin. According to these results, this enzyme has potential for use in the food and pharmacy industries since P. ulaiense does not produce mycotoxins.

Optimization, production and scale up of debittered kinnow beverage by and #945;-L-rhamnosidase producing yeast

“…Maximum naringinase production (12.05 UL -1 ) was observed at 34 h of fermentation, which corresponds to a stationary phase of growth (Mukund et al, 2014). In the batch reactor, the maximum α-rhamnosidase activity was obtained after 10 days from Penicillium ulaiense (Rajal et al, 2009). The reduction in production time is important because it decreases the fermentation costs and contamination with opportunistic microorganisms in scale up process.…”

“…Aliquots of 50 µL from the reaction mixture were removed every 2 min and placed into 1.5 mL of 0.5 M NaOH. These aliquots were kept in an ice bath until the absorbance was measured at 400 nm (Rajal et al, 2009). One unit (U) of enzyme activity was defined as the amount of enzyme required to release 1 μmol of p-nitrophenol per minute.…”

Evaluation and characterization of new α-L-rhamnosidase-producing yeast strains

“…Aliquots of 50 µL from the reaction mixture were removed from the growth medium every 2 min and placed into 1.5 mL of 0.5 M NaOH. These aliquots were kept in an ice bath until the absorbance was measured at 400 nm (Rajal et al, 2009). Enzyme characterization.…”

“…The reduction in fermentation time is important because it decreases the fermentation costs and contamination with opportunistic microorganisms in a scale-up process (Rajal et al, 2009). …”

Organic and Inorganic Salts as Postharvest Alternative Control Means of Citrus

“…Rots from field infection include Alternaria rot, Phytophthora rot, Phomopsis and Diplodia stem-end rot, has been described on citrus fruit in the United States [9,10], Australia [12], Argentina [13], and recently in Egypt [14] and Tunisia [15]. Besides the taxonomic and phytopathological aspects [8,10], there is little or no information about this organism [16].…”