BF5-EXPLOITATION OF AGRO-INDUSTRIAL RESIDUES FOR HYDROLYTIC ENZYMES PRODUCTION AND WATER RECOVERY OF THE BIOPROCESS

TATARÍN, ANA SILVIA; VELÁZQUEZ, JUAN ERNESTO; BENÍTEZ, SILVANA FLORENCIA; SADAÑOSKI, MARCELA ALEJANDRA; FONSECA, MARÍA ISABEL

Córdoba

Congreso; XVII Congreso Argentino de Microbiología General; 2022

Sociedad Argentina de Microbiología General SAMIGE

The use of agro-industrial residues in culture media composition are reported as low-cost substrates for production of different fungal enzymes. Nevertheless, this process consumes high quantity of water, which could be reused. The aim of the present study was to evaluate the hydrolytic enzyme production through agro-industrial residues from sugar and citrus industry and the toxicity of water recovers from the bioprocess. Three biotreatments were carried out in 500 mL Erlenmeyer flasks containing 300 mL of natural medium in buffer 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 14 d of incubation to enzymatic activity determination. Aqueous phase extracted by vacuum vaporization was used to phytotoxicity evaluation. Xilanase activity (XA) was assayed using beechwood xylan. Reducing sugars obtained were 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 obtained were determined by DNS method. Amylase activity was expressed in units (U) like XA.Proteolytic activity (PA) was revealed by the milk plate method in Petri dishes containing powdered skim milk 1% w/v and agar 1% w/v diluted in sodium acetate buffer pH 4.8. Samples were placed in wells and incubated at 37±1 °C for 24 h. PA activity was expressed as the area of the clarification zones (mm2). Gelatinase activity (GA) was determined by same method than PA but Petri dishes containing 1% w/v gelatin-agar. For phytotoxicity assays, twelve seeds were placed in sterile Petri plates with Whatman paper containing 2 mL of aqueous phase recovered by vacuum vaporization. Petri plates were incubated at 24 ± 1°C in darkness, during 120 h. Then, 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) for treatment 3. AA, at 7 d, was maximum (2139.19 ± 1354,25 U/L) for treatment 3. At 14 d, AA was maximum (1102.38 ± 284.62 U/L) for treatment 1. At 7 d, PA was maximum (53.14 ± 5.20 mm2) for treatment 2 and at 14 d, PA was maximum (66.45±5.26 mm2) for treatment 3. GA activity was maximum 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. GP for untreated waste orange peel was 0%. These results suggest that sugarcane bagasse and orange peel residues are suitable substrates to hydrolytic enzyme production and that it is possible to recovery the water of the bioprocess with acceptable toxicity levels for treatment 1 and 2.