Microbial community study of brine evaporation ponds: identification and analysis of the total organic carbon problem.

Abstract

Salt is an important compound as it is used by humans for everyday life. Salt production can occur from two processes: the use of seawater which is evaporated leaving the salt behind or the use of brine which is obtained from underground sources and undergoes the same process of evaporation as the seawater. The focus for this research will be on the microorganism population in salt produced from underground brine sources such as the source used by Botswana Ash (Pty) Ltd (Botash) which is the salt works that provided the samples for this research paper. The most important microorganism found in salt evaporation ponds is the green algae Dunaliella salina (D. salina) as discovered by previous studies. The main focus of this study was the identification of the microorganisms that are found within the salt evaporation ponds and the effect that the dominant D. salina population will have on the salt production process and also whether the dominant D. salina species can be used for production of important by-products to generate another source of income. The population genetics study on the samples from the various evaporation ponds at Botash has revealed the presence of many different microorganisms such as the bacterium Salinabacter, and the green algae Dunaliella salina which was revealed to be the dominant species. Other species such as archaea were also discovered within the salt evaporation ponds at Botash. The green algae D. salina was focused upon due to its dominance within the higher salinity ponds where it serves as the primary producer. The growth rate of the dominant D. salina species was observed in different conditions such as saline concentrations and different nitrogen sources. The results found that D. salina grows best at 3M salinity with NO3 or Urea as the nitrogen source. A study of the growth of D. salina when environmental factors were controlled showed that D. salina prefers high temperatures and high saline conditions for growth. D. salina also produces high value products such as beta carotene and Extra Polysaccharides (EPS). The production of these compounds are linked to the environmental conditions as it was found that beta carotene production is optimized when the cells are placed under stress during nitrogen starvation. EPS production occurs under all environmental conditions. The results from this research paper show that if the microbial community is controlled and optimized useful by-products can be produced, whilst minimal harm is done to the quality of salt produced.