Citric acid is currently produced by submerged fermentation of sucrose with the aid of Aspergillus niger mold. Its strains are characterized by a high yield of citric acid biosynthesis and no toxic by-products. Currently, new substrates are sought for production of citric acid by submerged fermentation. Waste materials such as glycerol or pomace could be used as carbon sources in the biosynthesis of citric acid. Due to the complexity of the metabolic state in fungus, there is an obvious need to optimize the important medium constituents to enhance the accumulation of desired product. Potential optimization approach is a statistical method, such as the central composite rotatable design (CCRD). The aim of this study was to increase the yield of citric acid biosynthesis by Aspergillus niger PD-66 in media with waste glycerol as the carbon source. A mathematical method was used to optimize the culture medium composition for the biosynthesis of citric acid. In order to maximize the efficiency of the biosynthesis of citric acid the central composite, rotatable design was used. Waste glycerol and ammonium nitrate were identified as significant variables which highly influenced the final concentration of citric acid (Y₁), volumetric rate of citric acid biosynthesis (Y₂), and yield of citric acid biosynthesis (Y₃). These variables were subsequently optimized using a central composite rotatable design. Optimal values of input variables were determined using the method of the utility function. The highest utility value of 0.88 was obtained by the following optimal set of conditions: waste glycerol—114.14 g∙L⁻¹and NH₄NO₃—2.85 g∙L⁻¹.

The gluten-free food market has become one of the fastest-growing food markets for food intolerances. People with celiac disease, gluten intolerance, non-celiac gluten sensitivity, and other gluten-related diseases should follow a gluten-free diet. The demand for gluten-free products is growing yearly, mainly due to the increasing number of diagnosed cases. The aim of the study was to assess consumers’ knowledge of gluten-free foods and covered people of all ages, and was conducted using a questionnaire. The research results indicate that most consumers have a lot of knowledge concerning gluten-free food. Moreover, most consumers know what gluten is and what products to avoid while on a gluten-free diet. They also know which diseases it causes and that it is necessary to follow a diet, but they have difficulty determining the acceptable gluten content in gluten-free products. Consumers’ most crucial parameter when choosing a gluten-free product is taste. The results of the survey also show that a gluten-free diet is more popular among women than men.

Nauki Inżynierskie i Technologie = Engineering Sciences and Technologies, 2022, Nr 38, s. 27-40