Revisiting the Single Cell Protein Application of Cupriavidus necator H16 and Recovering Bioplastic Granules Simultaneously

Abstract

Cupriavidus necator H16 (formerly known as Hydrogenomonas eutropha) was famous as a potential single cell protein (SCP) in the 1970s. The drawback however was the undesirably efficient accumulation of non-nutritive polyhydroxybutyrate (PHB) storage compound in the cytoplasm of this bacterium. Eventually, competition from soy-based protein resulted in SCP not receiving much attention. Nevertheless, C. necator H16 remained in the limelight as a producer of PHB, which is a material that resembles commodity plastics such as polypropylene. PHB is a 100% biobased and biodegradable polyester. Although tremendous achievements have been attained in the past 3 decades in the efficient production of PHB, this bioplastic is still costly. One of the main problems has been the recovery of PHB from the cell cytoplasm. In this study, we showed for the first time that kilogram quantities of PHB can be easily recovered in the laboratory without the use of any solvents and chemicals, just by using the cells as SCP. In addition, the present study also demonstrated the safety and tolerability of animal model used, Sprague Dawley given lyophilized cells of C. necator H16. The test animals readily produced fecal pellets that were whitish in color, as would be expected of PHB granules. The pellets were determined to contain about 82-97 wt% PHB and possessed molecular mass of around 930 kg/mol. The PHB granules recovered biologically possessed similar molecular mass compared to chloroform extracted PHB [950 kg/mol]. This method now allows the production and purification of substantial quantities of PHB for various experimental trials. The method reported here is easy, does not require expensive instrumentation, scalable and does not involve extensive use of solvents and strong chemicals.

Production and recovery of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) from biodiesel liquid waste (BLW)

“…Mealworm has been recently reported for their ability to degrade polystyrene (PS) and two PS‐degrading bacterial strains were isolated from the mealworm gut . The remarkable findings of of the ability of mealworm in extracting PHAs granules has led to this study. Mealworms are omnivorous insects that can grow on low‐quality feeds such as organic wastes .…”

“…Nowadays, researchers have developed other methods to reduce solvents level, chemicals used, and time. Many alternative methods were developed such as surfactant‐based extraction methods , low frequency sonic waves , chemical disruption, enzymatic digestion, and biological recovery . Biological recovery is a relatively recent and unconventional method that feeds certain animals with PHA‐containing bacterial cells and recovers PHA granules from the PHA‐enriched feces .…”

Polyhydroxyalkanoate production in biofermentor monitored through biosensor application

“…Several approaches have been proposed to make the process economically convenient. For instance, single cell protein method allows fermentation and recovery of granules in a single passage; [34][35][36] there are various lysis methods available, 26,37 based on alkaline treatment, before PHA recovery. 38 All these protocols are economically convenient and environmentally friendly, not requiring the use of solvents such as chloroform.…”

Comparison of acid and enzymatic hydrolysis of pectin, as inexpensive source to cell growth of Cupriavidus necator

“…necator was famous as a potential single cell protein (SCP) in the 1970s, studies evaluated that bacterial cells would average 50.0% protein, with 93.0% of digestibility by animals and high concentration of important amino acids similar to those found in casein. However, the competition from soybased protein resulted in SCP not receiving much attention, but in recent years has resurgence the interest in SCP and PHA as a component of animal feed to increase the metabolizable energy content (Kunasundari et al 2013).…”