Potential of utilizing almond hull extract for filamentous fungi production by submerged cultivation

Almond hulls can be used as an inexpensive source of nutrients for producing fungi that can be used as nontraditional foods such as alternative protein, probiotics, and food ingredients. Nutrients were extracted from almond hulls using hot water and their utility in cultivating filamentous fungus Aspergillus awamori (A. awamori) in submerged cultivation was investigated using batch fermentation in flasks with passive aeration. The almond hulls extract supplied all the nutrients required for A. awamori growth. The uptake preference of various sugars was investigated and the growth kinetic parameters of A. awamori were determined. Utilization of sugars by A. awamori grown in almond hull extract proceeded sequentially with preference for glucose followed by sucrose, fructose, and then xylose. Compared to potato dextrose broth medium, the fungal biomass produced using almond hull extract as growth medium had higher protein (19.59%) and lower fat (1.50%) contents. The modified Gompertz model described the kinetics of A. awamori well with a lag phase of 0.18 days and a specific growth rate of 1.77 d⁻¹.