PHB Production in Biofermentors Assisted through Biosensor Applications

Abstract

Polyhydroxyalcanoates (PHAs) are biodegradable polymers synthesized in cytoplasmic granules in bacteria, such as Cupriavidus necator (Ralstonia eutropha), Alcaligenes latus, Pseudomonas spp., Comamonas spp. and other species. PHAs accumulation occurs in response to stress conditions, i.e. under high carbon and low nitrogen (24:1 ratio). PHA can be synthesized using recombinant microorganisms (provided with the operon phbA/phbB/phbC), escaping the constrains of nutrient request, except addition of high amount of sugar (glucose, lactose, fructose). In this study; E. coli was genetically modified for PHB production in biofermentors. The production of PHA at industrial scale requires a continuous supplementation of fermentable sugars to support the availability of nutrients and to assess the level of the exponential growth phase; since sugars are required either for bacterial growth either for PHA synthesis and energy storage. The biofermentors need to be run in automated system. Sensors are used at many points in fermentators; in the evaluation of parameters: consumption of sugars; cell density; quantification of PHB synthesis. The need of operational control during the fermentation has prompted us to application of three measurements; one unit linked to a Nanodrop to evaluate OD; one linked to a reaction chamber to measure sugars consumed by enzyme based fluorescence detection; and one for bacteria Nile Blue staining and fluorescence intensity reads. The growth of bacteria on three different plant by-products was monitored and PHB production in four days using a banana by-product feed was optimised. These detectors will make possible to exploit the full potential of bioreactors optimizing the time of use and maximizing the number of bacteria synthesizing PHA.

Polyhydroxyalkanoate production in biofermentor monitored through biosensor application

“…26 A quantitative measure of PHA producing bacteria has been based on fluorescence scale reads using a laser scanner. 31 (Figure 1) In our hands, the system showed an optimization of feed stock consumption and determination of feed supplementation during exponential growth that occurred contemporary to PHB synthesis, while at the stationary phase determination of maximum PHB presence allowed to stop the biofermentor without further supplementation of feeds. In this way, we obtained an improvement of bacteria growth phase monitoring, in respect to the available systems.…”

“…Finally, solid PHB/PHA is obtained by non-solvent (methanol and water 7:3vol/vol) precipitation (five volumes for each volume of chloroform) followed by filtration. 31…”

Microalgal Biorefinery Concepts’ Developments for Biofuel and Bioproducts: Current Perspective and Bottlenecks

“…Another study reported that the Chlamydomonas reinhardtii triglycerol was molded as bioplastic beads that could withstand 1.7 MPa of compressive stress [ 73 ]. Acetate and citrate supplementation in the media is another strategy to improve the PHB production in cyanobacteria and microalgal cells [ 74 ]. Strain improvement such as mutation and genetic modification of key enzymes involved in the PHB synthesis pathway can enhance PHB production [ 75 ].…”

Green synthesis of polyhydroxyalkanoate polymer by Bacillus iocasae

“…A sample was collected from a station (activated sludge) located at Pajam, Shubra El-Kheima, Qalyubia, Egypt. For bacterial isolation, 11 the sludge sample was serially diluted up to 10 −6 . 100 μL from each dilution was cultured on carbon-rich nutrient agar medium composed of 10 g L −1 glucose, 8 g L −1 NaCl, 5 g L −1 peptone, 3 g L −1 yeast extract and 15 g L −1 agar; 19 the pH was adjusted to 7 using 1 mol L -1 NaOH and 30% HCl.…”

“…2 The formation of the polymer is mainly associated with the stationary phase of many bacterial strains such as Bacillus cereus, Bacillus subtilis, Brevibacterium halotolerance and Pseudomonas aeruginosa [8][9][10] ; acetyl coenzyme A (acetyl-CoA), the intermediate of the central carbon metabolism, is required for cell synthesis during the exponential phase but is diverted to produce PHAs in the stationary phase. 11 PHA granules are made up of a hydrophobic, amorphous polymeric core enclosed by a single layer of phospholipids as well as protein molecules. 12 These proteins involve the PHA synthase and intracellular PHA depolymerase.…”