Deconvoluting algal and bacterial biomass concentrations in algal-bacterial suspensions

Algae and algal-bacterial consortia have many applications including biofuel production, as source of many beneficial products, and in wastewater treatment. With increasing interest in such systems, a suitable method to estimate the individual biomass concentrations of algae and bacteria in a mixed suspension is still not available. The objective of this study was to develop a method for estimating the algal and bacterial concentrations in suspensions containing both algae and bacteria. The method involved (1) determination of algal number concentration in the algal-bacterial suspension through manual algal cell counting, (2) conversion of the algal number concentration to algal mass concentration by applying a consolidated conversion factor, and (3) determination of bacterial mass concentration in the suspension by subtracting the algal mass concentration from the gravimetrically determined total biomass concentration in the suspension. Using the protocols developed in this study, algal biomass concentrations estimated in purely algal or artificially constituted algal-bacterial suspensions were comparable, both in terms of mean values and precision, to the corresponding algal biomass concentrations determined through direct gravimetric measurements. Estimations of algal and bacterial biomass concentration in suspensions with unknown algae and bacteria concentrations are also reported.