Search

Microalgae are a natural source of lipids, carotenoids, and other value-added compounds. The combination of nutrients and their precise ratio have a significant impact on the productivity of microalgae-mediated compounds. The biomass, lipid, chlorophyll, and carotenoid production of three microalgae species, namely, Monoraphidium sp., Chlorella sorokiniana, and Scenedesmus obliquus, were investigated by employing standard photoautotrophic media, namely, BG-11, BBM, and HS CHU-10. BBM was found as the most effective medium since it obtained higher biomass, lipids, and carotenoids from microalgae. The lipids and carotenoids were identified using chromatographic and microscopy techniques. The findings showed that although the Monoraphidium sp. biomass productivity was the lowest, it emerged as a substantial producer of astaxanthin, whereas the Chlorella sorokiniana culture could grow in a variety of media and produced β-carotene as a major carotenoid. On the other hand, Scenedesmus obliquus was found to be a considerable source of lipids and β-carotene. This study provided a comprehensive understanding of the appropriate medium selection in order to extract an assortment of value-added compounds from freshwater microalgae species. [ABSTRACT FROM AUTHOR]

Recently, CRISPR-Cas9-based genome editing has been widely used for plant breeding. In our previous report, a tomato gene encoding hybrid proline-rich protein 1 (HyPRP1), a negative regulator of salt stress responses, has been edited using a CRISPR-Cas9 multiplexing approach that resulted in precise eliminations of its functional domains, proline-rich domain (PRD) and eight cysteine-motif (8CM). We subsequently demonstrated that eliminating the PRD domain of HyPRP1 in tomatoes conferred the highest level of salinity tolerance. In this study, we characterized the edited lines under several abiotic and biotic stresses to examine the possibility of multiple stress tolerance. Our data reveal that the 8CM removal variants of HK and the KO alleles of both HK and 15T01 cultivars exhibited moderate heat stress tolerance. Similarly, plants carrying either the domains of the PRD removal variant (PR1v1) or 8CM removal variants (PR2v2 and PR2v3) showed better germination under osmosis stress (up to 200 mM mannitol) compared to the WT control. Moreover, the PR1v1 line continuously grew after 5 days of water cutoff. When the edited lines were challenged with pathogenic bacteria of Pseudomonas syringae pv. tomato (Pto) DC3000, the growth of the bacterium was significantly reduced by 2.0- to 2.5-fold compared to that in WT plants. However, the edited alleles enhanced susceptibility against Fusarium oxysporum f. sp. lycopersici, which causes fusarium wilt. CRISPRCas9- based precise domain editing of the SlHyPRP1 gene generated multistress-tolerant alleles that could be used as genetic materials for tomato breeding. [ABSTRACT FROM AUTHOR]

Abstract Background E. coli is a robust host for various genetic manipulations and has been used commonly for bioconversion of hexose and pentose sugars into valuable products. One of the products that E. coli make under fermentative condition is ethanol. However, availability of limited reducing equivalence and generation of competing co-products undermine ethanol yield and productivity. Here, we have constructed an E. coli strain to produce high yield of ethanol from hexose and pentose sugars by modulating the expression of pyruvate dehydrogenase and acetate kinase and by deleting pathways for competing co-products. Results The availability of reducing equivalence in E. coli was increased by inducing the expression of the pyruvate dehydrogenase (PDH) operon under anaerobic condition after replacement of its promoter with the promoters of ldhA, frdA, pflB, adhE and gapA. The SSY05 strain, where PDH operon was expressed under gapA promoter, demonstrated highest PDH activity and maximum improvement in ethanol yield. Deletion of genes responsible for competing products, such as lactate (ldhA), succinate (frdA), acetate (ack) and formate (pflB), led to significant reduction in growth rate under anaerobic condition. Modulation of acetate kinase expression in SSY09 strain regained cell growth rate and ethanol was produced at the maximum rate of 12 mmol/l/h from glucose. The resultant SSY09(pZSack) strain efficiently fermented xylose under microaerobic condition and produced 25 g/l ethanol at the maximum rate of 6.84 mmol/l/h with 97% of the theoretical yield. More importantly, fermentation of mixture of glucose and xylose was achieved by SSY09(pZSack) strain under microaerobic condition and ethanol was produced at the maximum rate of 0.7 g/l/h (15 mmol/l/h), respectively, with greater than 85% of theoretical yield. Conclusions The E. coli strain SSY09(pZSack) constructed via endogenous pathway engineering fermented glucose and xylose to ethanol with high yield and productivity. This strain lacking any foreign gene for ethanol fermentation is likely to be genetically more stable and therefore should be tested further for the fermentation of lignocellulosic hydrolysate at higher scale.