(763c) Alternative WATER Treatment Using Cactus Mucilage From Opuntia SPP.: Application in Bacteria Removal

Daniela Stebbins, Dawn Fox, Audrey Buttice, Deni-Maire Smith Norma Alcantar

Department of Chemical & Biomedical Engineering, University of South Florida

Cholera is a rapidly dehydrating, diarrheal causing disease that can kill within hours if left untreated and affects millions of people every year (WHO 2011). The cholera outbreak in Haiti that followed a powerful earthquake in 2010 motivated this study. Our purpose is to investigate an alternative treatment to remove bacteria from water using a natural biomaterial that can be used by communities in need. The mucilage is produced by several cacti species. The specie that we are using is the Opuntia ficus-indica, commonly known as Nopal or Prickly pear cactus. The Nopal cactus pads are readily available, inexpensive and have been used to clean water by ancient communities in Mexico. Extensive research in our group has shown that the mucilage is efficient at removing turbidity, bacteria (E. coli and Bacillus sp.) and arsenic from contaminated water. Now we are investigating the conditions under which cactus mucilage will be able to reduce the levels of a surrogate for Vibrio Cholerae, named Vibrio furnissii. Lyophilized pellets of the surrogate bacteria were purchased from a testing laboratory specialized in environmental and public health threats. The pellets were suspended in Marine Broth following specification from the vendors, transferred to Marine Agar and kept at 4 °C until the experiments were performed. A single colony, incubated at 35 °C for 24 hours, was transferred to 5 mL of Marine Broth and kept in a shaker incubator for 24 hours at 35 °C. A 1 mL aliquot was diluted in 4 mL of Marine broth and kept in the same conditions for more 2 hours. The bacteria suspension was washed once in PBS to remove extracellular metabolites. The pellet was re-suspended in 50 mL of PBS and used as spike solution to set up water columns where the mucilage was tested. The final bacteria concentration in the testing water columns (10 mL) was ~ 10⁶ cells. We have tested 3 concentration of the mucilage (0, 1 and 10 mg/L), with and without 10 mg/L of calcium carbonate in three repetitions. The experiments were conducted at room temperature and columns were left undisturbed for 2 hours. Aliquots of 1 mL were taken from the top of the experimental water columns and homogenized with a vortex. Four serial dilutions were placed and sub-aliquots of 100 µL were plated and incubated at 35 °C for 24 hours to plate count and to establish the mucilage removal abilities. Although the higher concentration of the mucilage (10 mg/L) did not decrease the bacteria concentration, the lower concentration of the mucilage (1 mg/L) removed 25% of the original concentration of the bacteria on the top of the water column. The treatment using 1 mg/L of mucilage plus calcium carbonate was determined to remove 40% of the bacteria. These preliminary studies suggest that mucilage from the Opuntia ficus-indica is a viable flocculation method for Cholera. Its low cost, accessibility, and current use as a food source in low income communities give mucilage great potential as a water treatment method for areas such as Haiti that have had devastating bacterial contaminations.