Spray Drying Is a Viable Technology for the Preservation of Recombinant Proteins in Microalgae

Real-time monitoring method of microbial growth using a simple pressure-based respiration detection system

Dry cell weight (DCW) and optical density (OD) measurement methods provide useful data for assessing microbial growth. However, their sampling process is labor-intensive and time-consuming. Therefore, we aimed to evaluate a method for measuring microbial growth through continuous CO2 measurement under aerobic conditions using a pressure-based respiration detection system, which is traditionally used in anaerobic environments and applies measurement of reduced pressure by capturing CO2 with KOH. The pressure reduction rate, OD, and DCW values were compared during Ralstonia eutropha H16 culture, which revealed a correlation of R2 of 0.99 between the pressure reduction and DCW and a change of DCW (g/L) per pressure (1 mbar) of -0.02 g/L. It showed theoretical limit of detection at 14.67 mbar corresponding to 0.0428 g/L of DCW and theoretical limit of quantification at 48.9 mbar as lower limits. When the pressure-based method was applied to compare carbon source utilization and growth of different strains, such as E. coli sp., Pseudomonas sp., Burkholderia sp., and Bacillus sp., it showed a high correlation with DCW. Overall, these results demonstrate that the pressure-based respiration detection system is a reliable tool for microbial growth monitoring and offers significant advantages by providing real-time data with less labor.

The Clinical Promise of Microalgae in Rheumatoid Arthritis: From Natural Compounds to Recombinant Therapeutics

Rheumatoid arthritis (RA) is an invalidating chronic autoimmune disorder characterized by joint inflammation and progressive bone damage. Dietary intervention is an important component in the treatment of RA to mitigate oxidative stress, a major pathogenic driver of the disease. Alongside traditional sources of antioxidants, microalgae-a diverse group of photosynthetic prokaryotes and eukaryotes-are emerging as anti-inflammatory and immunomodulatory food supplements. Several species accumulate therapeutic metabolites-mainly lipids and pigments-which interfere in the pro-inflammatory pathways involved in RA and other chronic inflammatory conditions. The advancement of the clinical uses of microalgae requires the continuous exploration of phytoplankton biodiversity and chemodiversity, followed by the domestication of wild strains into reliable producers of said metabolites. In addition, the tractability of microalgal genomes offers unprecedented possibilities to establish photosynthetic microbes as light-driven biofactories of heterologous immunotherapeutics. Here, we review the evidence-based anti-inflammatory mechanisms of microalgal metabolites and provide a detailed coverage of the genetic engineering strategies to enhance the yields of endogenous compounds and to develop innovative bioproducts.

Transgenic Microalgae Expressing Double-Stranded RNA as Potential Feed Supplements for Controlling White Spot Syndrome in Shrimp Aquaculture

Viral infection of farmed fish and shellfish represents a major issue within the aquaculture industry. One potential control strategy involves RNA interference of viral gene expression through the oral delivery of specific double-stranded RNA (dsRNA). In previous work, we have shown that recombinant dsRNA can be produced in the chloroplast of the edible microalga Chlamydomonas reinhardtii and used to control disease in shrimp. Here, we report a significant improvement in antiviral dsRNA production and its use to protect shrimp against white spot syndrome virus (WSSV). A new strategy for dsRNA synthesis was developed that uses two convergent copies of the endogenous rrnS promoter to drive high-level transcription of both strands of the WSSV gene element in the chloroplast. Quantitative RT-PCR indicated that ~119 ng dsRNA was produced per liter of culture of the transgenic microalga. This represents an ~10-fold increase in dsRNA relative to our previous report. The engineered alga was assessed for its ability to prevent WSSV infection when fed to shrimp larvae prior to a challenge with the virus. The survival of shrimp given feed supplemented with dried alga containing the dsRNA was significantly enhanced (~69% survival) relative to a negative control (<10% survival). The findings suggest that this new dsRNA production platform could be employed as a low-cost, low-tech control method for aquaculture.