A comparative study of the producti

A comparative study of the production of neutral protease was carried out by the cultivation of
Aspergillus oryzae NRRL 2220 in solid-state fermentation (SSF) and submerged fermentation (SmF) using
tomato pomace based medium. For this purpose, medium optimization was achieved using two
experimental designs. The first, corresponded to the Plackett and Burman design with N = 8 experiments
and k = N  1 factors; five real (wheat bran, casein, NH4NO3, NaCl and ZnSO4) and two errors. Statistical
analysis of the results allowed the selection of two factors having a significant effect on enzyme
production (casein and NaCl in SSF, wheat bran and NaCl in SmF). Optima of the selected factors have
been determined through a second experimental design, the central composite design of Box and Wilson
with two factors; 19.79 g/L casein and 0.92 g/L NaCl for SSF and 17.92 g/L wheat bran and 1.18 g/L NaCl
for SmF were found. The optimal production time of the neutral protease determined from the kinetic
study was 96 h leading to 21309 U/g in SSF and 2343.5 U/g in SmF. The comparison of the proteolytic
activities of the optimized media demonstrated a ratio of 9 between SSF and SmF, showing the efficiency
of the solid-state fermentation compared to the submerged fermentation. The results confirmed the high
biotechnological potential of this fungal strain for neutral protease production in solid-state
fermentation. Additionally, the utilization of tomato pomace constitutes an efficient and inexpensive
agro industrial substrate for protease production via the SSF approach and a suitable mean for its
valorization and to reduce its ecological impact.