In a paper appearing this week in ACS Central Science, a journal of the American Chemical Society, UC Berkeley’s Omar Yaghi and his colleagues describe the latest version of their water harvester, which can pull more than five cups of water (1.3 liters) from low-humidity air per day for each kilogram (2.2 pounds) of water-absorbing material, a very porous substance called a metal-organic framework, or MOF. That is more than the minimum required to stay alive.

During field tests over three days in California’s arid Mojave Desert, the harvester reliably produced 0.7 liters per kilogram of absorber per day — nearly three cups of clean, pure H2O. That’s 10 times better than the previous version of the harvester. The harvester cycles 24/7, powered by solar panels and a battery.

Even on the driest day in the desert, with an extremely low relative humidity of 7% and temperatures over 80 degrees Fahrenheit, the harvester produced six ounces (0.2 liters) of water per kilogram of MOF per day.

“It is well known that in order to condense water from air at a low humidity — less than 40 percent relative humidity — you need to cool down the air to below freezing, to zero degrees Celsius, which is impractical. With our harvester, we are doing this at very low humidity without such cooling; there is no other material that can do that,” said Yaghi, a UC Berkeley professor of chemistry and co-director of the Kavli Energy NanoSciences Institute. “This is not like a dehumidifier, which operates at high relative humidity. Some people say that 0.7 liters is not a lot of water. But it is a lot of water, if you don’t have water.”

Yaghi’s startup, Water Harvester Inc., is now testing and will soon market a device the size of a microwave oven that can supply 7 to 10 liters of water per day: enough drinking and cooking water for two to three adults per day, based on recommendations from the National Academy of Sciences that men should consume 3.7 liters and women 2.7 liters of fluid per day.

An even larger version of the harvester, one the size of a small refrigerator, will provide 200 to 250 liters of water per day, enough for a household to drink, cook and shower. And in a couple of years, the company hopes to have a village-scale harvester that will produce 20,000 liters per day. All would run on power from solar panels and a battery or off the electrical grid.

“We are making ultra-pure water, which potentially can be made widely available without connection to the water grid,” said Yaghi, the James and Neeltje Tretter Chair in the College of Chemistry. “This water mobility is not only critical to those suffering from water stress, but also makes possible the larger objective — that water should be a human right.”

The key: highly porous MOFs

The harvester’s secret ingredient is a type of MOF invented by Yaghi and his UC Berkeley colleagues that easily and quickly takes up water from the air and just as readily disgorges it so the water can be collected. MOFs, which Yaghi has been developing since the mid-1990s, are so porous that a gram has a surface area equivalent a football field. Other types of MOFs capture carbon dioxide from flue gases, catalyze chemical reactions or separate petrochemicals in processing plants.

The researchers came up with their first water-absorbing MOF, called MOF-801, in 2014. Water molecules in ambient air stick to the internal surface — a process called adsorption — and increase the humidity inside the MOF to a point where the water condenses even at room temperature, just as water condenses on cooler surfaces when the humidity is high. When the MOF is heated slightly, the water comes back out and can be condensed and collected.

The first harvester employing MOF-801 premiered in 2017 and was totally passive and solar powered: It sat and adsorbed water at night and gave it up the next day in the heat of the sun, with the water vapor condensing on the inside surface of the container.

By 2018, Yaghi’s Berkeley team had turned that proof-of-concept device into a second-generation harvester that collected 0.07 liters — a little over 2 ounces — of water per day per kilogram of MOF during one day-night cycle in the Arizona desert, again using heat from the sun to drive the water out of the MOF.

“Although the amount of water was low, the experiment showed how water from desert air can be concentrated into the pores of the MOF, removed by mild heating with sunlight and then condensed at ambient conditions,” Yaghi said.

The 2019 model is no longer passive: It uses solar panels to power fans blowing ambient air over MOF contained within a cartridge, so that more of the MOF is exposed to air. The MOF-filled cartridge, about 10 inches square and 5 inches thick, is intersected by two sets of channels: one set for adsorbing water, the other for expelling it to the condenser, allowing continuous cycling throughout the day. The solar panels, attached to batteries so that the harvester can run at night, also power small heaters that drive the water out of the MOF.

The productivity of this new water harvester is 10 times the amount harvested by the previous device and 100 times higher than the early proof-of-concept device. No traces of metal or organics have been found in the water.

The improved productivity and shorter cycling time of the new device comes from a newly designed MOF, MOF-303, that is based on aluminum, as opposed to MOF-801, which is based on zirconium. MOF-303 can hold 30% more water than MOF-801 and can adsorb and desorb water in a mere 20 minutes under ideal conditions — something Yaghi’s startup is close to achieving.

“MOF-303 does two things very well: It takes up much more water than the zirconium MOF we reported on before, and it does it much faster,” Yaghi said. “This allows water to go in and out much faster; you can pump air in and harvest the water over many cycles per day.”

Yaghi gets inquiries about his harvester nearly every day from people, agencies and countries around the world, many in arid regions of the Middle East, Africa, South America, Mexico, Australia and around the Mediterranean. The bulk of the funding for improvements to the harvester comes from Saudi Arabia’s King Abdulaziz City for Science and Technology, as part of a joint KACST-UC Berkeley collaboration called the Center of Excellence for Nanomaterials and Clean Energy Applications. Desert kingdoms chronically short on water appreciate the harvester’s potential, said Yaghi, who comes from another arid country, Jordan.

“The atmosphere has almost as much water at any one time as all the rivers and lakes,” he said. “Harvesting this water could help turn dry deserts into oases.”

Klebsiella pneumoniae causes a variety of infections including rare but life-threatening liver, respiratory tract, bloodstream and other infections. Little is known about how exactly people become infected, and the bacteria are unusually adept at acquiring resistance to antibiotics. The prototype vaccine, details of which are published online Aug. 27 in Proceedings of the National Academy of Sciences, may offer a way to protect people against a lethal infection that is hard to prevent and treat.

“For a long time, Klebsiella was primarily an issue in the hospital setting, so even though drug resistance was a real problem in treating these infections, the impact on the public was limited,” said co-author David A. Rosen, MD, PhD, an assistant professor of pediatrics and of molecular microbiology at Washington University. “But now we’re seeing Klebsiella strains that are virulent enough to cause death or severe disease in healthy people in the community. And in the past five years, the really resistant bugs and the really virulent bugs have begun to merge so we’re beginning to see drug-resistant, hypervirulent strains. And that’s very scary.”

Hypervirulent strains of Klebsiella caused tens of thousands of infections in China, Taiwan and South Korea last year, and the bacteria are spreading around the world. About half of people infected with hypervirulent, drug-resistant Klebsiella die. Two types in particular — known as K1 and K2 — are responsible for 70 percent of the cases.

Rosen; senior author Christian Harding, PhD, a co-founder of VaxNewMo; first author Mario Feldman, PhD, an associate professor of molecular microbiology at Washington University and a co-founder of VaxNewMo; and colleagues decided to create a vaccine against the two most common strains of hypervirulent Klebsiella. The bacterium’s outer surface is coated with sugars so the researchers designed a glycoconjugate vaccine composed of these sugars linked to a protein that helps make the vaccine more effective. Similar vaccines have proven highly successful at protecting people against deadly diseases such as bacterial meningitis and a kind of pneumonia.

“Glycoconjugate vaccines are among the most effective, but traditionally they’ve involved a lot of chemical synthesis, which is slow and expensive,” Harding said. “We’ve replaced chemistry with biology by engineering E. coli to do all the synthesis for us.”

The researchers genetically modified a harmless strain of E. coli, converting it into tiny biological factories capable of churning out the protein and sugars needed for the vaccine. Then they used another bacterial enzyme to link the proteins and sugars together.

To test the vaccine, the researchers gave groups of 20 mice three doses of the vaccine or a placebo at two-week intervals. Then they challenged the mice with about 50 bacteria of either the K1 or the K2 type. Previous studies had shown that just 50 hypervirulent Klebsiella bacteria are enough to kill a mouse. In contrast, it takes tens of millions of classical Klebsiella — the kind that affects hospitalized people — to be similarly lethal.

Of the mice that received the placebo, 80 percent infected with the K1 type and 30 percent infected with the K2 type died. In contrast, of the vaccinated mice, 80 percent infected with K1 and all of those infected with K2 survived.

“We are very happy with how effective this vaccine was,” Feldman said. “We’re working on scaling up production and optimizing the protocol so we can be ready to take the vaccine into clinical trials soon.”

The goal is to get a vaccine ready for human use before the hypervirulent strains start causing disease in even larger numbers of people.

“As a pediatrician, I want to see people get immunity to this bug as early as possible,” Rosen said. “It’s still rare in the United States, but given the high likelihood of dying or having severe debilitating disease, I think you could argue for vaccinating everybody. And soon we may not have a choice. The number of cases is increasing, and we’re going to get to the point that we’ll need to vaccinate everybody.”

“This represents a new treatment for inherited breast and ovarian cancer, which are higher in our region,” said Robert A. Hromas, M.D., FACP, professor and dean of the Joe R. and Teresa Lozano Long School of Medicine at UT Health San Antonio. Dr. Hromas is senior investigator on the research, published in the journal Proceedings of the National Academy of Sciences. (Reference: “MiR223-3p promotes synthetic lethality in BRCA1-deficient cancers,” Aug. 8, 2019.)

A tiny molecule called microRNA (miR) 223-3p prevents normal cells from making mistakes while repairing their DNA. However, cancers with BRCA1 mutations repress miR223-3p to permit their cells to divide. Adding back miR223-3p forces the BRCA1-mutant cancer cells to die, said study co-author Patrick Sung, D. Phil. Dr. Sung, who joined UT Health San Antonio in 2019 from Yale, is a BRCA1 cancer expert who occupies the Robert A. Welch Distinguished Chair in Biochemistry.

Exploiting the cancer’s Achilles’ heel

MiR223-3p acts like a light switch, turning off proteins that BRCA1-mutant cancers need to divide properly. Without these key cell division proteins, BRCA1-mutant tumors commit suicide, Dr. Hromas said.

“It’s kind of a cool way of thinking about treatment,” Dr. Hromas said. “We are using the very nature of these BRCA1-deficient cancer cells against them. We are attacking the very mechanism by which they became a cancer in the first place.”

There is evidence that restoring miR223-3p before cells convert to cancer can even prevent BRCA1-related disease, he said.

BRCA gene mutations affect 1 in every 400 people in the United States — an estimated 825,000. After Ashkenazi Jews, Hispanics have the second-highest prevalence of BRCA1 disease-causing mutations. The disease’s burden in San Antonio and South Texas is therefore among the highest in the country.

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Materials provided by University of Texas Health Science Center at San Antonio. Note: Content may be edited for style and length.