Fed-batch production of a bioflocculant from Corynebacterium glutamicum

Abstract

The constant-rate fed-batch production of the polygalacturonic acid bioflocculant REA-11 was studied. A controlled sucrose-feeding strategy resulted in a slight improvement in biomass and a 7% reduction in flocculating activity compared with the batch process. When fed with a 3 g l(-1) urea solution, the flocculating activity was enhanced to 720 U ml(-1) in 36 h. High cell density (2.12 g l(-1)) and flocculating activity (820 U ml(-1)) were obtained in a 10-l fermentor by feeding with a sucrose-urea solution, with values of nearly two times and 50% higher than those of the batch process, respectively. Moreover, the residual sucrose declined to 2.4 g l(-1), and residual urea decreased to 0.03 g l(-1). Even higher flocculating activity of 920 U ml(-1) and biomass of 3.26 g l(-1) were obtained by feeding with a sucrose-urea solution in a pilot scale fermentation process, indicating the potential industrial utility of this constant-rate feeding strategy in bioflocculant production by Corynebacterium glutamicum.

Characterization of an Exopolymeric Flocculant Produced by a Brachybacterium sp.

“…This is corroborated by the decline of bioflocculant production as viable cell density declined. The reports of Wu et al [7] and Lu et al [21] are in corroboration with these observations. In addition, the decline in medium pH would be attributed to organic acids produced by the organism, or better still, the metabolites had more of an acidic moieties, hence decreasing the pH of the medium.…”

“…Additionally, magnesium chloride was the best cation source, with flocculation activity of about 91.1% ± 1.18% with a yield of 4.66 ± 1.19 g/L. On a similar note, nutritional requirements, which include glucose, fructose, sucrose, urea, ammonium sulfate, calcium and magnesium, have been reported to optimally support various bacteria for the production of bioflocculant [7,8,15]. …”

“…They are thus generally categorized into three: inorganic flocculants, organic synthetic polymeric flocculants and the flocculants of microbial origin, known as a bioflocculant [6,7,8]. The inorganic flocculants and the organic synthetic polymeric flocculants have enjoyed wider application, due to cost effectiveness and higher flocculation efficiency [9,10].…”

A Freshwater Streptomyces, Isolated from Tyume River, Produces a Predominantly Extracellular Glycoprotein Bioflocculant

“…Flocculants are categorized into three groups, namely the inorganic flocculants which includes salts of aluminum (aluminum sulfate and poly-aluminum chloride); the organic synthetic polymeric flocculants (polyacrylamide derivatives and polyethylene imines), and the natural occurring flocculants of microbial origin, termed bioflocculant, which includes chitosan and sodium alginate [5–7]. The inorganic and organic synthetic polymeric flocculants are widely used in industrial processes as they possess high efficiency of flocculation and are inexpensive [6,8]; however associated demerits have been colossal and it includes deleterious health problems such as cancer and neuro-toxicity in the case of polyacrylamide derivatives and polyethylene imines and Alzheimer’s disease with respect to salts of aluminum [9–11].…”

Studies on Bioflocculant Production by Arthrobacter sp. Raats, a Freshwater Bacteria Isolated from Tyume River, South Africa

“…The high cost of production coupled with low yield seem to be the major deterring factors in the advancement of research in developing bioflocculants for both scientific and commercial applications [7]. However, in order to reduce costs and optimize cultivation conditions, strategies such as fed-batch production processes are being developed [8]. …”