Measuring changes in concentration within a dynamic system can be accomplished with a simple Arduino powered system. Currently, the system is utilized in cyanobacteria CO2 fixation experiments, where the fixation rates of multiple cultures can be measured simultaneously. The system employs solenoids in parallel and can be applied for n number of outlet streams, all are connected to one large manifold which feeds to a CO2 concentration probe. In the future, the system can be modified to fit other simple dynamic gas systems.
The production of sustainable biochemicals has been a major topic of discussion in recent years. Using microbial cells for their production through genetic engineering has been a major topic of research. Cyanobacteria have been considered as a viable candidate for such production. However, the slow growth rate of the cells presents a challenge for the possibility of scaling for use in industrial settings. This project focuses on two different solutions for this problem. The first is using four different engineered strains of Synechocystis sp. PCC 6803 that overexpress the proteins in the b6f complex to improve photosynthetic efficiency. It was found that the strains PetB and PetD showed an increase in growth rate compared to wild type cells. This was especially true under mixotrophic conditions and with a light intensity of 100 µmol photons*m-2s-1 for 3 days. The second solution is by using a newly discovered marine strain of cyanobacteria, Synechococcus sp. PCC 11901, which has a higher reported growth rate. Higher growth rates were achieved for this strain when it was grown mixotrophically with glycerol, and when grown in bubble cultures with aeration.
Cyanobacteria and microalgae help reduce the environmental impact of human energy consumption by playing a vital role in carbon and nitrogen cycling. They are also used in various applications like biofuel production, food, medicine, and bioremediation. Understanding how these organisms respond to stress is important for efficient recovery strategies and sustainable outcomes. This study investigated the effects of low-level bleaching and thermal stress on cyanobacteria and microalgae, specifically Synechocystis, Chlorella, and Scenedesmus. The role of ferroptosis, an iron-dependent form of cell death, in the degradation of cellular components under these stressors was examined. Flow cytometry and spectrophotometry were used to measure changes in cellular health and viability. The results showed that temperature influences the type of cell death mechanism and can impact photosynthetic organisms. When treated with Liproxstatin-1, an inhibitor of ferroptosis, both Synechocystis and Chlorella experienced a decrease in oxidative damage, suggesting a potential protective role for the compound. Further investigation into ferroptosis and other forms of cell death, as well as identifying additional inhibitory molecules, could lead to strategies for mitigating oxidative stress and enhancing the resilience of cyanobacteria and microalgae.
Improving cyanobacterial hydrogen production through bioprospecting of natural microbial communities
Finally, results interpretation was severely hampered by a lack of appropriate systematic treatment for an important group of biocrust cyanobacteria, the “Microcoleus steenstrupii complex”. I characterized the complex using a polyphasic approach, leading to the formal description of a new family (Porphyrosiphonaceae) of desiccation resistant cyanobacteria that includes 11 genera, of which 5 had to be newly described. Under the new framework, the distribution and abundance of biocrust cyanobacteria with respect to environmental conditions can now be understood. This body of work contributes significantly to explain current distributional patterns of biocrust cyanobacteria and to predict their fate in the face of climate change.
During the initial phase of the study, I integrated a membrane filter with a bench-top photobioreactor (PBR) and created a continuously operating system. Recycling permeate reduced the amount of fresh medium delivered to the PBR by 45%. Biomass production rates as high as 400 mg-DW/L/d (9.2 g-DW/m2/d) were sustained under constant lighting over a 12-day period.
In the next phase, I operated the system as a sequencing batch reactor (SBR), which improved control over nutrient delivery and increased the concentration factor of filtered biomass (from 1.8 to 6.8). I developed unique system parameters to compute the amount of recycled permeate in the reactor and the actual hydraulic retention time during SBR operation. The amount of medium delivered to the system was reduced by up to 80%, and growth rates were consistent at variable amounts of repeatedly recycled permeate. The light-based model accurately predicted growth when biofilm was not present. Coupled with mass ratios for PCC 6803, these predictions facilitated efficient delivery of nitrogen and phosphorus. Daily biomass production rates and specific growth rates equal to 360 mg-DW/L/d (8.3 g/m2/d) and 1.0 d-1, respectively, were consistently achieved at a relatively low incident LI (180 µE/m2/s). Higher productivities (up to 550 mg-DW/L/d) occurred under increased LI (725 µE/m2/s), although the onset of biofilm impeded modeled performance.
Permeate did not cause any gradual growth inhibition. Repeated results showed cultures rapidly entered a stressed state, which was followed by widespread cell lysis. This phenomenon occurred independently of permeate recycling and was not caused by nutrient starvation. It may best be explained by negative allelopathic effects or viral infection as a result of mixed culture conditions.