A major challenge to the economic viability of outdoor cultivation of microalgae is the high cost of CO2 supply, even when microalgae farms are co-located with point sources of CO2 emissions. In addition, the global capacity for algae biofuel generation is severely restricted when microalgae farm locations are constrained by proximity to CO2 sources along with the additional limitations of low slope lands and favorable climate. One potential solution to the impediments of CO2 supply cost and availability is through cultivation of microalgae in highly alkaline pH solutions (pH >10) that are effective at scavenging CO2 from the atmosphere at high rates. The extremely alkaline pH media would also mitigate culture crashes due to microbial contamination and predators. In this study, we report the indoor and outdoor phototrophic cultivation of a microalgae isolate (Chlorella sorokiniana str. SLA-04) adapted to grow in unusually high-pH environments. The isolate was cultivated in a growth medium at pH >10 without any inputs of concentrated CO2. Both indoor and outdoor studies showed biomass and lipid productivities that were comparable to those reported for other microalgae cultures cultivated in near-neutral pH media (pH 7–8.5) under similar conditions. SLA-04 cultures also showed high lipid productivity and high glucose-to-lipid conversion efficiency when cultivated mixotrophically in the presence of glucose as an organic carbon source. From the energy content (calorific value) of the lipids produced and glucose consumed, a relatively high amount of lipid calories (0.62) were produced per glucose calorie consumed. In conclusion, our results demonstrate the feasibility of microalgae cultivation in extremely high-pH media (pH >10) as a novel strategy for biofuel production without dependence on concentrated CO2 inputs.

The aim of this investigation was to study the efficacy of UV-C light emitting diode system (LED) operating at 263 nm for the inactivation of Listeria monocytogenes and Escherichia coli O157:H7. Specified concentrations of bacteria were inoculated in apple juice and irradiated at the designated UV doses of 0 to 15 mJ/cm-2. In addition, UV irradiation doses ranging from 0 to 160 mJ/cm-2 were also delivered to apple juice and polyphenols and vitamins were profiled. LC-MS/MS analysis was conducted to assess the stability of polyphenols or vitamins in UV-C exposed apple juice. The polyphenol and vitamin results demonstrated that UV-C irradiation in apple juices at relevant commercial UV doses induced significant reductions in the concentrations of selected polyphenols and vitamins, p<0.05. Ascorbic acid was reduced to 32%, at 160 mJ/cm2 whereas 17% reduction was observed at 40 mJ/cm2. Riboflavin was observed to be relatively stable. Epicatechin and chlorogenic was significantly reduced at high exposure doses. In contrast minor changes were observed at 40 mJ/cm2. Results show that UV-C irradiation effectively inactivated pathogenic microbes in apple juice. The log reduction kinetics of microorganisms followed log-linear and with higher R2 (>0.95) and low RMSE values. The D10 values of 4.16 and 3.84 mJ/cm-2 were obtained from the inactivation of Escherichia coli, and Listeria monocytogenes in apple juice. The results from this study imply that adequate log reduction of pathogens is achievable in apple juice and suggest significant potential for UV-C treatment of other liquid foods.

Outdoor cultivation of microalgae for biofuel production is not yet economically feasible, in part due to costs associated with CO2 supply. Large point sources of CO2 are also rarely available in proximity to desired large-scale algae cultivation sites (nonagricultural, barren, and flat lands). The cost and location constraints posed by concentrated CO2 supply can be avoided by cultivation of microalgae that have the ability to grow under extreme alkaline pH conditions (pH > 10). These alkaline solutions are effective at scavenging atmospheric CO2 at high rates and, in addition, afford natural protection for desired alkaliphilic microalgae cultivars against common competing organisms and predators. In this study, we report the cultivation of an extreme alkaliphilic microalgae isolate, Chlorella sorokiniana str. SLA-04 in a high pH (pH > 10) medium that also contains a high carbonate/bicarbonate alkalinity (>100 mequiv·L–1). This medium design simultaneously provides (i) a high driving force to effectively scavenge atmospheric CO2 due to the high medium pH and (ii) nonlimiting bicarbonate concentrations (>20 mM) for photosynthetic carbon fixation. We demonstrated high biomass productivities (>16 g·m–2·d–1) in 4.2 m2 raceway ponds by using this medium and without addition of concentrated CO2 (i.e., using atmospheric CO2 alone). Experimental measurements and theoretical mass transfer calculations show that rates of CO2 uptake into the medium from the ambient atmosphere matched or exceeded the rates of dissolved inorganic carbon uptake due to photosynthesis. Further, measured lipid productivities were either higher or comparable to those reported for other raceway pond microalgae cultivations that used concentrated CO2 sparging. This is the first study to report high biomass and lipid productivities of phototrophic microalgae cultures sustained with atmospheric CO 2 alone.

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Severe Acute Respiratory Syndrome coronavirus-2 (SARS-CoV-2) is responsible for the COVID-19 pandemic that continues to pose significant public health concerns. While research to deliver vaccines and antivirals are being pursued, various effective technologies to control its environmental spread are also being targeted. Ultraviolet light (UV-C) technologies are effective against a broad spectrum of microorganisms when used even on large surface areas. In this study, we developed a pyrimidine dinucleotide frequency based genomic model to predict the sensitivity of select enveloped and non-enveloped viruses to UV-C treatments in order to identify potential SARS-CoV-2 and human norovirus surrogates. The results revealed that this model was best fitted using linear regression with r 2 = 0.90. The predicted UV-C sensitivity ( D 90 – dose for 90% inactivation) for SARS-CoV-2 and MERS-CoV was found to be 21.5 and 28 J/m 2 , respectively (with an estimated 18 J/m 2 obtained from published experimental data for SARS-CoV-1), suggesting that coronaviruses are highly sensitive to UV-C light compared to other ssRNA viruses used in this modeling study. Murine hepatitis virus (MHV) A59 strain with a D 90 of 21 J/m 2 close to that of SARS-CoV-2 was identified as a suitable surrogate to validate SARS-CoV-2 inactivation by UV-C treatment. Furthermore, the non-enveloped human noroviruses (HuNoVs), had predicted D 90 values of 69.1, 89, and 77.6 J/m 2 for genogroups GI, GII, and GIV, respectively. Murine norovirus (MNV-1) of GV with a D 90 = 100 J/m 2 was identified as a potential conservative surrogate for UV-C inactivation of these HuNoVs. This study provides useful insights for the identification of potential non-pathogenic (to humans) surrogates to understand inactivation kinetics and their use in experimental validation of UV-C disinfection systems. This approach can be used to narrow the number of surrogates used in testing UV-C inactivation of other human and animal ssRNA viral pathogens for experimental validation that can save cost, labor and time.