Applications of Microalgal Biotechnology for Disease Control in Aquaculture

Abstract

Aquaculture industries, and in particular the farming of fish and crustaceans, are major contributors to the economy of many countries and an increasingly important component in global food supply. However, the severe impact of aquatic microbial diseases on production performance remains a challenge to these industries. This article considers the potential applications of microalgal technology in the control of such diseases. At the simplest level, microalgae offer health-promoting benefits as a nutritional supplement in feed meal because of their digestibility and high content of proteins, lipids and essential nutrients. Furthermore, some microalgal species possess natural anti-microbial compounds or contain biomolecules that can serve as immunostimulants. In addition, emerging genetic engineering technologies in microalgae offer the possibility of producing ‘functional feed additives’ in which novel and specific bioactives, such as fish growth hormones, anti-bacterials, subunit vaccines, and virus-targeted interfering RNAs, are components of the algal supplement. The evaluation of such technologies for farm applications is an important step in the future development of sustainable aquaculture.

The phosphite oxidoreductase gene, ptxD as a bio-contained chloroplast marker and crop-protection tool for algal biotechnology using Chlamydomonas

“…The NNV transformant is part of an on-going 'proof-of-concept' project as a cheap, oral vaccine for the farmed fish industry (Charoonnart et al 2018). However, production of algal biomass for applications such as feed additives for the aquaculture, poultry and other livestock sectors, can be challenging, not least because of the problems of contamination in low-cost photobioreactor systems (Taunt et al 2017).…”

Advances and challenges in genetic engineering of microalgae

“…Nevertheless, there have been several reports that highlighted the potential of using chloroplast engineering to create custom strains to produce functional feed additives (Charoonnart et al . ; Khan et al . ).…”

“…Currently, most algal transgenics involve the use of constitutive promoters, expressing the recombinant gene during algal biomass production, which can negatively impact growth, either because of the extra metabolic burden or because of a toxic effect on the cell (Charoonnart et al 2018). Thus, a better strategy is to induce gene expression towards the end of the growth phase, by using tightly regulated promoters with a large dynamic range, together with effective codon optimization, improving the efficiency of growth and the final productivity of the desired gene product.…”

“…C. reinhardtii is the only microalgal species for which chloroplast transformation is currently well established, although there are isolated reports of transformation of several other species including D. tertiolecta and P. tricornutum (Dyo & Purton 2018). Nevertheless, there have been several reports that highlighted the potential of using chloroplast engineering to create custom strains to produce functional feed additives (Charoonnart et al 2018;Khan et al 2018).…”

Validation of a New Multicistronic Plasmid for the Efficient and Stable Expression of Transgenes in Microalgae

“…Although in recent years, an increasing number of microalgal species have been successfully transformed and important goals have been accomplished, the genetic transformation of microalgae has still important pending challenges. Both, the low stability of the transgenes and the high variability of their expression levels among the obtained transformants, make necessary large screenings to select high-expression stable clones [10][11][12]. In fact, low nuclear expression of transgenes in microalgae has hampered the efficient and stable engineering of metabolic pathways and has limited the use of these microorganisms for the commercial production of recombinant proteins.…”