bacterial-cellulose-spheres-that-encapsulate-solid-materials

Bacterial Cellulose Spheres that Encapsulate Solid Materials

Bacterial cellulose (BC) spheres have been increasingly researched since the popularization of BC as a novel material. This protocol presents an ...

Montana Technological University

As demand for clean water increases, there is a growing need for effective sustainable water treatment systems. We used the symbiotic culture of bacteria and yeast (SCOBY) that forms while brewing kombucha tea as a living water filtration membrane (LFM). The LFMs function as ultrafiltration membranes with a permeability of 135 ± 25 L m h bar and a 90% rejection of 30 nm nanoparticles. Because they contain living microorganisms that produce cellulose fibers, the surface of an LFM heals after a puncture or incision. Following punctures or incisions, membrane permeability, after a rapid increase postpuncture, returns to 110-250% of the original flux after 10 days in a growth solution. Additionally, LFMs may be manufactured using readily available materials, increasing membrane production accessibility.

Sustainable Living Filtration Membranes.

Living Filtration Membranes (LFMs) are a water filtration technology that was recently developed in the lab (Technology Readiness Level 4). LFMs have shown filtration performance comparable with that of ultrafiltration, far better fouling resistance than conventional polymer membranes, and good healing capabilities. These properties give LFMs promise to address two significant issues in conventional membrane filtration: fouling and membrane damage. To integrate environmental considerations into future technology development (i.e., Ecodesign), this study assesses the life cycle environmental performance of drinking water treatment using LFMs under likely design and operation conditions. It also quantitatively ranks the engineering design and operation factors governing the further optimization of LFM environmental performance using a global sensitivity analysis. The results suggest that LFMs' superior fouling resistance will reduce the life cycle environmental impacts of ultrafiltration by 25% compared to those of a conventional polymer membrane in most impact categories (e.g., acidification, global warming potential, and carcinogenics). The only exception is the eutrophication impact, where the need for growth medium and membrane regeneration offsets the benefits of LFMs' fouling resistance. Permeability is the most important factor that should be prioritized in future R&D to further improve the life cycle environmental performance of LFMs. A 1% improvement in the permeability will lead to a ∼0.7% improvement in LFMs' environmental performance in all the impact categories, whereas the same change in the other parameters investigated (e.g., LFM lifespan and regeneration frequency) typically only leads to a <0.2% improvement.

Permeability is the Critical Factor Governing the Life Cycle Environmental Performance of Drinking Water Treatment Using Living Filtration Membranes.

Water filtration membranes produced sustainably through microbial cellulose production can have filtration properties altered through facile chemical treatments. Microbial cellulose is an effective membrane filtration medium, and pristine microbial membranes can serve as ultrafiltration membranes with a permeability of 143 L mhbar and a particle size cut off of 35 nm. As living biofilms, these membranes consist of microbial cellulose, bacteria, and extracellular polymers. Thus, additional biofilm components may reduce the intrinsic permeability of the cellulose. Here, microbial membranes were treated with hydrogen peroxide (HO) and sodium hypochlorite (NaOCl, liquid bleach) to remove impurities present in microbial cellulose and increase membrane permeability. For example, permeability increased from 143 to 257 L mhbar with treatment by 0.3% HO for 12 min. The membranes were also treated with sodium hydroxide (NaOH) to increase membrane selectivity, and the particle size cutoff was reduced from 35 to 10 nm post-treatment with 0.8% NaOH for 20 min. Scanning electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, contact angle goniometry, and X-ray diffraction were used to characterize the physical and chemical properties of the membrane matrix. Facile chemical treatments provide a significant degree of flexibility to tailor microbial membranes to meet specific needs. Microbial membrane production is inherently accessible, and this study furthers that accessibility by utilizing only readily available components to treat microbial membranes and expand their potential applications.

Facile Postprocessing Alters the Permeability and Selectivity of Microbial Cellulose Ultrafiltration Membranes.

Though germicidal UV radiation is widely applied for disinfection of water and food, it may also be used to prevent bacterial growth and colonization on surfaces within engineered systems. Emerging UV source technologies, such as ultraviolet-C (UVC) LEDs, present new opportunities for deterring biofilms within certain devices, including medical equipment, food equipment, and potentially in plumbing fixtures for prevention of opportunistic respiratory pathogen infections. Rational design for incorporation of UVC sources into devices with complex internal geometries is currently hampered by the lack of an engineering framework for predicting reductions in biofilm growth rates in response to continuous low-intensity irradiation. Herein we have developed an experimental apparatus and method for growing biofilms under concurrent UV irradiation and quantifying the resulting suppression of surface growth. Under accelerated growth conditions over 48 h, E. coli surface biovolume was reduced by 95% compared to control biofilms (grown in the dark) by a UV intensity of 50.5 µW/cm (254 nm). The required intensity for biofilm prevention was higher than expected, given the UV dose response of the bacteria employed and the cumulative doses delivered to the test surfaces. The results indicate that biofilms can establish even under irradiation conditions that would result in complete inactivation of planktonic cells, likely due to the shielding effects of colloidal material and microbial exudates. A pseudo-mechanistic model was also developed which correlated UV intensity to the resultant reduction in specific surface biovolume.

Katherine R. Zodrow

Department of Environmental Engineering

Montana Technological University

Bacterial Cellulose Spheres that Encapsulate Solid Materials