Browsing by Author "Khelifa, Halima"
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- Assessment of bacterial cellulose biosynthesis from olive bagasse using photostimulationPublication . Khelifa, Halima; Crujeira, Pedro Jorge Louro; Rodrigues, Paula; Noureddine, HallaThe biosynthesis of bacterial cellulose (BC) is an innovative approach with a variety of applications. Strategies have been studied to economically enable the process, with the most common being research on fermentation media to overcome limitations and increase competitiveness in the market, thus allowing greater diversity in the use of this biopolymer. Moist olive pomace (MOP) is a byproduct of the olive oil industry that can be phytotoxic to soil and water bodies, potentially causing environmental impact. This study aimed to evaluate BC production with various concentrations of MOP (1%, 5%, 10%, 20%, 30%, and 40%) and analyze the effect of LED irradiation at 630 ± 10 nm, depositing an energy density of 14 J/cm². Komagataeibacter intermedius SB14, a cellulose-producing strain, was identified and studied for BC production. The characterization of cellulose membranes was performed using Fourier- transform infrared spectroscopy (FTIR), thermogravimetric analysis, mechanical testing, and evaluation of antioxidant and antimicrobial activity. A significant increase (p < 0.0001) in BC production was observed in the 20% MOP group, with a 166.95% increase compared to the control (0% MOP). The result indicated a cellular response due to stress caused by the phenolic compounds present, leading to increased BC production. LED light emission led to a significant increase in BC production, with 124% in the control group and 392% in the 20% MOP group. Characteristic cellulose groups were identified in all produced samples. Mechanical testing revealed greater tensile strength and deformation capacity of the cellulose membrane produced with 20% MOP (60.73 MPa and 0.696 mm/mm) compared to the control (12.75 MPa and 0.098 mm/mm), respectively. Although increased antioxidant activity was observed in the MOP- containing medium, no antimicrobial activity was detected in any of the produced samples. This work highlights a sustainable pathway by introducing MOP into the circular economy chain and leveraging LED irradiation in the bioprocess to enhance production and reduce costs.
- Bacterial cellulose biosynthesis in the presence of raw moist olive pomace: A green sustainable approach that enhances biopolymer production and propertiesPublication . Crugeira, Pedro; Khelifa, Halima; Barreira, Luísa; Halla, Noureddine; Barreiro, Filomena; Rodrigues, Paula; Peres, António M.; Schreiner, Tatiana B.; Schreiner, Tatiana B.In this study, the biosynthesis of bacterial cellulose (BC) by Komagataeibacter intermedius strain isolated from Kombucha tea in the presence of raw moist olive pomace (MOP) (concentration up to 40 % in the fermentation media) was studied. The BC membranes were characterized by their antioxidant activity, structural character- istics, crystallinity, thermal stability, and mechanical behavior. Using raw MOP activated the inherent activity of the phenolic compounds, leading to cellular adaptation under unfavorable conditions and increased BC pro- duction for all tested MOP concentrations (p < 0.0001). This led to a 166.61 % increase for the 20 % MOP group compared to the control (HS medium). For this sample, enhanced antioxidant activity (~40-fold higher than the control) was found, which might be associated with the molecular interactions established between hydroxyls of BC and phenolic compounds. Moreover, an increase of 603.03 % in strain capacity, and a 376.01 % improvement in stress at break compared to the control was observed. The study confirmed that BC can be synthesized using MOP in its natural state, supporting a sustainable circular economy while enhancing the biosynthesis of a value- added product. By reducing synthetic media and utilizing MOP, a greener bioprocess can be achieved, and BC’s applicability can be expanded.