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Lignin in Biological Systems
Published in Severian Dumitriu, Valentin Popa, Polymeric Biomaterials, 2020
Little attention has so far been paid to the utility in biological science of lignins, which have long been regarded as waste from the pulp industry. However, the existing information evidences that lignin and its derivatives have a multifunctional role in biological systems (antibacterials, antioxidants and photoprotectors, anticarcinogen, anti-HIV, and spermicide) influencing cell metabolism. Having in mind the polyphenolic character of lignins, one may suppose that the action of lignins is based on their interactions with cell surface at the level of membrane lipids. Thus, the action of lignins can be correlated with their molecular mass and hydroxyl group content by hydrophilic–hydrophobic interactions. At the same time, lignins can be transformed by different metabolic pathways into products (e.g., lignans) that can be useful for human and animal health.
Spray-freeze-drying for the Encapsulation of Food Ingredients and Biologicals
Published in S. Padma Ishwarya, Spray-Freeze-Drying of Foods and Bioproducts, 2022
In certain cases, stabilizers are added to the SFD feed formulation containing probiotic cells and wall material for an enhanced protective effect (Semyonov et al., 2010). This is relevant as the SFL method of atomization induces both thermal and osmotic stresses upon the probiotic cells. In the case of Lactobacillus paracasei, cell viability was reduced by the fusion between its cell membrane and denatured proteins, during encapsulation by spray-freeze-drying. But, addition of trehalose and maltodextrin as stabilizers in the feed formulation prevented viability loss during both the spray-freezing and freeze-drying stages of SFD. The protective effect of trehalose and maltodextrin is governed by vitrification, which is the transformation of feed material to glassy state below the glass transition line of state diagram. During conventional freezing, ample time is available for ice formation and freeze concentration such that the solution attains a nearly equilibrium state of maximal freeze concentration. Consequently, the unfrozen regions turn highly viscous to vitrify at this concentration (Engstrom et al., 2007). The aforementioned phenomenon holds true during the SFD encapsulation of probiotic cells as well, due to which water is immobilized in the vitrified viscous glass. The low mobility of water prevents loss of cell viability caused by damage to cell membrane and protein unfolding. The low molecular weight of trehalose further promotes the vitrification phenomenon by decreasing the size of water crystal in the inter-membrane space. Ultimately, changes in the physical state of the membrane lipids are prevented and mechanical stresses in membranes are lessened, all of which improves cell viability (Koster et al., 2000). Table 7.3 summarizes the processing parameters and particle size of probiotic encapsulates produced by SFD.
Effects of certain physical stresses on the composition of the membrane of bacteria implicated in food and environmental contamination
Published in International Journal of Environmental Health Research, 2022
SalmaKloula Ben Ghorbal, Rim Werhani, Chatti Abdelwaheb
Gamma-irradiation, which is an ionizing irradiation, has long been used for decontamination and/or sterilization of food products as for mushroom conservation (Da Silva 2012; Fernandes et al. 2016; Akhila et al. 2021), treatment of real pharmaceutical industry wastewater, combined with coagulation treatment (Changotra et al. 2019), efficient removal of chlorendic acid from natural water, associated with peroxymonosulfate treatment (Shah et al. 2016) and textile wastewater decontamination (Bhuiyan et al. 2016). Bacteria become resistant to ionizing-radiation, by developing adaptive mechanisms and this fact may affect gamma-irradiation efficiency regarding bacterial inactivation, especially when using low irradiation doses. Several studies have confirmed the role of DNA repairing abilities and enzymatic systems; whose are major protective mechanisms, in microbial adaptation after γ irradiation (Guan and Long 2020). Moreover, membrane adaptation was recently confirmed to play an important role in adaptation to several physical stressor factors. As reported by several works (Shigapova et al. 2005; Koyiloth and Gummadi 2022), the degree of fatty acyl desaturation of membrane lipids is considered to be a critical factor in membrane fluidity. The relation between fatty acyl desaturation and bacterial adaptation was reported for Pantoea agglomerans bacterium (Dussault et al. 2008). According to this study, FA composition of the pre-adapted strain showed an increase of UFA and then a reduction of SFA, following γ-radiation treatment. This is similar to the results of Lyu et al. (2017) who reported that γ-radiation treatment (0.080 kGy) had an obvious influence on the lipid profile of the membrane of Shewanella. putrefaciens with a decrease trend, especially for SFA, C14:0 and C16:0, but also for monounsaturated fatty acids (MUFA), C16:1, C17:1, C18:1, compared with untreated S. putrefaciens. It was also reported for Shewanella bacteria that the mechanism for their survival lies in that the high percentage of UFA in the bacterial membrane confers a better membrane fluidity, which in turn enhances its capability of adaptation under different environmental changes (Lyu et al. 2017).This unsaturation is also confirmed for Bacillus cereus and Salmonella Typhi, treated with a sublethal radiation dose of 1 kGy (Ayari et al. 2009) and for Pantoea agglomerans strain, isolated from irradiated carrots at two doses of 1 and 3,5 kGy. At 1kGy, the shift seemed to take place in the length of the FA chain itself. At 3,5kGy, the shift to a smaller carbon chain seemed to take place (Dussault et al. 2009).