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Selection and Improvement of Industrial Organisms for Biotechnological Applications
Published in Nduka Okafor, Benedict C. Okeke, Modern Industrial Microbiology and Biotechnology, 2017
Nduka Okafor, Benedict C. Okeke
Many parts of the world have desert or near desert conditions where water is in short supply. Added to this is the fact that salt used for treating ice in the winter finds its way into agricultural land. These factors create conditionswhich bring plants into conditions of water (drought) and salt stress. To survive under these conditions, many plants synthesize compounds known as osmoprotectants. They help the plant increase its water uptake as well as retain the water absorbed. Osmoprotectants include sugars alcohols and quaternary ammonium compounds. The quaternary ammonium compound betaine is a powerful osmoprotectant and the gene encoding it obtained from E. coli has enabled plants into which it was cloned survive drought better than un-engineered plants.
Plant Responses and Tolerance to Drought
Published in Hasanuzzaman Mirza, Nahar Kamrun, Fujita Masayuki, Oku Hirosuke, Tofazzal M. Islam, Approaches for Enhancing Abiotic Stress Tolerance in Plants, 2019
Sumit Jangra, Aakash Mishra, Priti, Kamboj Disha, Neelam R. Yadav, Ram C. Yadav
Osmoprotectants are the compatible solutes that act as osmolytes so that an organism can survive in adverse stress conditions. In plants, these get accumulated to increase the survival rate during stress conditions. Singh et al. (2015) called the osmoprotectants universal molecules which help in regulating cellular osmotic adjustments and thus play an important role in drought tolerance. Osmoprotectants include quaternary active compounds like betaines, sugars, amino acids, etc. Sequera-Mutiozabal et al. (2017) had reported the role of polyamines (aliphatic organic compound) signaling during stress (drought and soil salinity) conditions. Tiburcio et al. (2014) had stated the function of polyamines in the life of a plant from its developmental stage to the stress conditions. Researchers have reported the role of many polyamines like putrescine (Put) (Espasandin et al., 2014), spermidine (Spd), and spermine (Spm) (Seyedsalehi et al., 2017) in plants for stress tolerance. Qin et al. (2017) developed transgenic soybeans by inserting BADH gene AcBADH from drought-tolerant Atriplex canescens into soybean cv. Jinong 17 by Agrobacterium-mediated transformation method. The transgenic plants were found to have enhanced tolerance to drought stress compared to non-transgenic plants. Also, proline content was increased by 12.5% to 16.6%, and peroxidase activity was increased to 7% from 1% in transgenic plants under drought stress as compared to non-transgenic plants. Duque et al. (2016) demonstrated that when oat Adc (Arginine decarboxylase) gene was introduced into Medicago truncatula through Agrobacterium-mediated transformation, the transgenic plants were found to have higher contents of polyamines viz. spermine, putrescine and norspermidine as compared to normal plants and were more tolerant to water deficit conditions. Adc gene is essential for the synthesis of polyamine. Transgenic plants had the ability to avoid tissue dehydration and also had increased photosynthetic rate under drought conditions. Ke et al. (2016) reported that when glycine betaine synthesizing gene cod A (choline deoxygenase) was expressed in transgenic poplar plants, transgenic plants gave tolerance to drought stress by accumulating higher content of GB as compared to normal poplar plants. Some of the plants engineered with osmoprotectants to mitigate drought stress are listed in Table 4.3.
The response of three typical freshwater algae to acute acid stress in water
Published in Journal of Environmental Science and Health, Part A, 2022
Xing Ma, Xuan Chen, Jiangtao Fan, Yunzhong Wang, Jianfeng Zhang
Numerous previous studies have reported that salinity stress affects algae and plants through osmotic and ionic stresses, while algae can produce metabolites to protect against salt injury and to balance the surrounding osmotic stress. The production of osmoprotectants or compatible solutes lowers the internal water potential of the cell, thus enabling the cell to take up water from the environment. However, the synthesis of compatible solutes requires ATP and NADPH. As a result, trying to maintain proper osmotic conditions may therefore incur a high energy cost, which may be manifested as reduced growth rates and a decrease in photosynthetic electron transport activities. This pathway was confirmed by the changes in SOD activity and MDA content. According to different indicators (survival rate, Chl a, SOD, MDA), the order of acid tolerance of these three algae was different, as described in the above section. Although the survival rate was used as a direct indicator to reflect the tolerance of algae to acid stress in this study, the changes in indicators such as Chl a, SOD and MDA did not follow a consistent trend. We speculate that this may be attributed to differences in the structure and components of the three algal cells.
Novel hydroxyectoines based formulations are suitable for preserving viability of Limosilactobacillus fermentum, Levilactobacillus brevis SP-48 and Bifidobacterium lactis HN019 during freeze-drying and storage, and in simulated gastrointestinal fluids
Published in Drying Technology, 2023
Azza Dabous, Sergio D’ambrosio, Donatella Cimini, Chiara Schiraldi
Compatible solutes like trehalose, betaine, proline, and carnitine have gained great attention due to their effective role in helping the probiotics to cope with stresses associated with freeze-drying. In fact, the addition of these solutes enhanced the survival during freeze-drying,[10] due to their ability to partially substitute hydrogen bonding of water molecules, or through the so called “exclusion mechanism thereby preserving the integrity of cell membranes.[11] In fact, other studies revealed that the accumulation of compatible solutes can alleviate other stresses like heat stress, cold stress, and desiccation stress.[12] Like trehalose, ectoine, and its derivative 5-hydroxyectoine (5-Hydroxy-2-methyl-1,4,5,6-tetrahydropyrimidine-4-carboxylic acid) are typical representative of compatible solutes that are widely synthesized by (extremely) halophilic bacteria and a few Archaea and Eukarya in response to unfavorable growth conditions.[13] Ectoine was traditionally produced by Halomonas elongata through a “bacterial milking” process.[14] Several scientific efforts aimed to improve the feasibility of ectoine production.[15] Due to their safety as showed by animal and human studies, their applications are spread in the medical, cosmetics and biochemistry fields.[16] Recently, they have been used as cryopreservants for mammalian cells,[17,18] and proved to maintain the viability of air dried and freeze dried Escherichia coli.[19] Although the mechanism underlying this cryopreservation ability has not been fully unraveled yet, there are various hypothesis that suggest potential mechanisms of action through biophysical specific features. The “preferential exclusion paradigm,” according to which osmoprotectants do not interact directly with macromolecules in aqueous solutions but are repelled to the bulk region, enhancing macromolecule hydration, and thereby preventing denaturation of proteins and stabilizing the enzymatic activities, is the most frequently accepted hypothesis.[20] However, there is only one published study demonstrating the role of these solutes in the protection of probiotic bacteria during freeze drying alone or in combination with other cryoprotectant agents like trehalose.[21] Thus, the protective function of ectoine and HOE in comparison to trehalose as positive control were evaluated in the present study on established and potential probiotic strains for the first time up to date. Viability preservation of Limosilactobacillus fermentum, Levilactobacillus brevis SP-48 and Bifidobacterium lactis HN019, was studied during freeze drying and storage up to 6 months, in different conditions. After determining the optimal concentration for each solute, the ability of these matrixes to enhance the survivability of probiotics in simulated gastrointestinal conditions was also analyzed.