EXPLOITATION OF AGRO-INDUSTRIAL RESIDUES FOR HYDROLYTIC ENZYMES PRODUCTION AND WATER RECOVERY OF THE BIOPROCESS

TATARIN AS; VELÁZQUEZ JE; BENÍTEZ SF; SADAÑOSKI MA; FONSECA MI

Congreso; XVII Congreso Argentino de Microbiología General; 2022

The use of agro-industrial residues in culture media composition are reported as low-cost substratesfor production of fungal enzymes. However, this process consumes high quantity of water, whichcould be reused. The aim was to evaluate the hydrolytic enzyme production through agro-industrialresidues from sugar and citrus industry and the toxicity of water recovers from the bioprocess. Threebiotreatments were carried out in 500 mL Erlenmeyer flasks containing 300 mL of natural medium inbuffer acetate 0.1 N, pH 5.4, which were supplemented with: (1) sugarcane bagasse (15 g/L); (2)sugarcane bagasse (15 g/L) and orange peel (75 g); and (3) sugarcane bagasse (15 g/L) and orange peel(150 g). Erlenmeyer flasks were inoculated with 9 mL of Aspergillus niger LBM 055 spore suspension(5.2 x 106 spore/mL) and incubated at 28 ± 1 °C, 500 rpm, during 14 d. Samples were taken at 7 and 14d to enzymatic activity determination. Aqueous phase extracted by vacuum vaporization was used tophytotoxicity. Xilanase activity (XA) was assayed using beechwood xylan. Reducing sugars obtainedwere determined by the 3,5-dinitrosalycillyc acid (DNS) method. Activity was expressed in units (U),defined as the amount of enzyme needed to produce 1 μmol of reducing sugars per min at 50 °C.Amylase activity (AA) was determined using soluble starch as substrate. Reducing sugars obtainedwere determined by DNS method. AA was expressed in units (U) like XA. Proteolytic activity (PA) wasrevealed by the milk plate method in Petri dishes containing powdered skim milk 1% w/v and agar 1%w/v. Samples were placed in wells and incubated at 37 ± 1 °C for 24 h. PA activity was expressed asthe area of the clarification zones (mm2). Gelatinase activity (GA) was determined by same methodthan PA but Petri dishes containing 1% w/v gelatin-agar. For phytotoxicity, twelve seeds were placedin sterile Petri plates containing 2 mL of aqueous phase. Petri plates were incubated at 24 ± 1°C, during120 h. Germination percentage (GP) and vigor index (VI) were determined. At 7 d, XA was maximum(3673.56 ± 260.16-1 U/L) for treatment 1. At 14 d, XA was maximum (3135.29 ± 647.52 U/L) fortreatment 3. AA, at 7 d, was maximum (2139.19 ± 1354,25 U/L) for treatment 3. At 14 d, AA wasmaximum (1102.38 ± 284.62 U/L) for treatment 1. At 7 d, PA was maximum (53.14 ± 5.20 mm2) fortreatment 2 and at 14 d, PA was maximum (66.45±5.26 mm2) for treatment 3. GA activity wasmaximum at 7 and 14 d for treatment 2, with values of 230.80 ± 11.43 and 242.27 ± 0.24 mm2,respectively. Respect to phytotoxicity assays, GP and VI was 97% and 383.16 ± 62.72 for treatment 1,75% and 124.95 ± 11.29 for treatment 2 and 64% and 143.34 ± 13.36 for treatment 3, respectively. GPfor untreated waste orange peel was 0%. These results suggest that tested residues are suitablesubstrates to hydrolytic enzyme production and it is possible to recovery the water of the bioprocesswith acceptable toxicity levels for treatment 1 and 2.