Mona S. Ashoor 1*, Wafa Mohammed Asiri2, Amal Naif Alshammari1 and Dhouha Taib Jellali2
1Biology Department, University College of Al-Darb, Jazan University, Jazan, Saudi Arabia; 2Mathematics Department, University College of Al-Darb, Jazan University, Jazan, Saudi Arabia
*Corresponding Author: drmonasaad2013@gmail.com
Oxygen availability is a critical determinant of fungal biodegradation efficiency in lignocellulosic systems, particularly under large-scale or poorly aerated conditions. This study examined the physiological and metabolic responses of a locally isolated Aspergillus flavus strain during barley straw degradation under aerobic and oxygen-limited conditions over a 15-day incubation period. Biodegradation efficiency, cellulase activity, soluble carbohydrate and protein production were quantified, and structural alterations were evaluated using scanning and transmission electron microscopy. Secondary metabolites were qualitatively screened through chromatographic analysis. Statistical evaluation included Student’s t-test and first-order kinetic modeling. Aerobic cultivation resulted in significantly higher dry matter loss (43.7%) compared with oxygen-limited conditions (19.3%) (p<0.01). Cellulase activity under aerobic conditions was approximately 2.3-fold greater than under oxygen limitation. Ultrastructural analysis revealed cell wall thickening, mitochondrial alterations, and lipid body accumulation under reduced oxygen availability, indicating adaptive responses to metabolic constraint. Qualitative screening did not reveal detectable aflatoxin within the analytical limits applied. These findings demonstrate that oxygen availability governs enzymatic efficiency and metabolic output in A. flavus, while partial biodegradation capacity is retained under oxygen limitation. The study provides insight into fungal adaptation relevant to lignocellulosic biomass processing under heterogeneous aeration conditions. This study provides new insights into oxygen-mediated metabolic modulation in Aspergillus species under controlled fermentation conditions.