Ramangalingam Kirubagaran

In recent years, genetic engineering has witnessed a remarkable shift towards harnessing the potential of microalgae for various applications including enhanced biomass production, biofuel production, wastewater treatment and the synthesis of valuable bioactive compounds. Our previous study has proven that genetic modifications of Chlorella vulgaris Beijer. using random mutagenesis significantly enhanced the lipid content, making it more ideal for biofuel production in C. vulgaris. However, efficient genetic engineering tools are still lacking in their ability to simultaneously augment the overall production of biomass and bioactive compounds. The present review discusses the most recent tools and strategies that are used to engineer microalgal strains, from culturing to modern gene-editing techniques like Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and CRISPR associated protein 9 (CRISPR-Cas9). Numerous studies have reported that targeted nucleases represent a remarkable advancement in genome manipulation, offering unparalleled precision. A novel variant of CRISPR, known as CRISPRi technique was reported to yield significant outcomes in microalgal species even under non-stressful conditions. Further, to curtail the bottlenecks due to high guanine-cytosine contents of DNA in microalgae, a new approach such as Adaptive Single Guide Assisted Regulation DNA (ASGARD) was explored along with CRISPRi, which yielded higher lipid and protein contents, thus finding indispensable applications in industry. Hence, this review effectively conveys the advantages and disadvantages associated with various genetic engineering tools and the complexity and precision required in genetic modification and the resulting potential for improved biomass, lipid and bioactive compounds productivity in marine microalgal species.

Evaluating the effect of various environmental factors on the growth of the marine microalgae, Chlorella vulgaris

Toxic effects of continuous low dose application of the antifouling biocide chlorine on marine benthic organisms were monitored using transplanted green mussels (Perna viridis) and a suite of biomarkers. Caged mussels were deployed in chlorinated and non-chlorinated sections of the cooling system of an operating electric power plant. Biomarkers indicative of general stress, oxidative stress (superoxide dismutase and catalase), and DNA integrity, along with expression of stress proteins, were studied to assess the effects. Deterioration in condition index with corresponding increase in DNA strand breaks was indicative of chlorine stress. Superoxide dismutase enzyme did not show any particular trend, but catalase activity was high during the initial days of exposure at the chlorinated site; later, it became almost equal to that at the control site. Similarly, expressions of stress proteins (HSP60, HSP70, HSP22, GSTS1, and CYP4) showed bell-shaped pattern during the period of study. Positive correlation among the endpoints indicated the utility of the multimarker approach to monitor the effects of continuous low dose chlorination on mussels.

Aims: Marine macroalgae are the rich source of biologically active metabolites and potential source for development of novel biotechnological products. The present study was made to explore the metabolically active compounds from the macroalgae of the Andaman & Nicobar Islands. Methods and Material: Different solvents such as methanol (MeOH), ethyl acetate (EtoAc), butanol (BuOH) and aqueous (H 2 O) extracts of nine macroalgae were tested for antimicrobial, antibiofilm and cytotoxicity (brine shrimp larvae). Results: Out of the 36 extracts 27 extracts showed antimicrobial activity against the human pathogens and 14 extracts revealed antibiofilm activities. The three EtoAc extracts of Sargassum ilicifolium, MeOH extract of Sargassum sp. and MeOH extract of Padina tetrastromatica showed inhibition against 8 pathogenic bacteria. Also, aqueous extract of Padina tetrastromatica (71.82 %) and BuOH extract of Dictyosphaeria cavernosa (71.58 %) exhibited higher antibiofilm nature. The highest cytotoxic effect was exhibited by species Actinotrichia fragilis and all its four extracts significantly (P<0.01) inhibited the brine shrimp larvae, among this aqueous extract showed the lowest LC 50 value, 31.7 µg/ml, followed by EtoAc extract, 89.33 µg/ml. Conclusion: It was observed that different species have different kind of bioactive nature.