Large-scale cultivation of synechocystis sp. PCC6803 for the production of poly(3-hydroxybutyrate) and its potential applications in the manufacturing of bulk and medical prototypes.

Polyhydroxyalkanoates (PHAs) are bioplastics produced by microorganisms under nutrient limiting conditions and in the presence of excess carbon source. PHAs have gained popularity as a sustainable alternative to traditional plastics. However, large scale production of PHAs is economically challenging due to the relatively high costs of organic carbon. Alternative options include using organisms capable of phototrophic or mixotrophic growth. This study aimed at the production of poly(3-hydroxybutyrate) P(3HB), a type of PHA, at pilot scale using the freshwater cyanobacterium Synechocystis sp. PCC6803. First, to identify optimal conditions for P(3HB) production from Synechocystis sp. PCC6803, different supplemental carbon source concentrations and salinity levels were tested at laboratory scale. The addition of 4g/L acetate with no added NaCl led to P(3HB) accumulation of 10.7% dry cell weight on the 28th day of cultivation. Although acetate additions were replicated in an outdoor 400L serpentine photobioreactor, P(3HB) content was lower, implying uncontrolled conditions impact on biopolymer production efficiency. An optimized P(3HB) extraction methodology was developed to remove pigments, and the biopolymer was characterized and subjected to 3D printing (fused deposition modelling) to confirm its processability. This study thus successfully led to the large-scale production of P(3HB) using sustainable and environmentally friendly cyanobacterial fermentation

Utilization of calcareous fly ash with Lopburi calcined clay as high Portland cement replacement supplementary cementitious materials

Calcined clay and calcareous fly ash were used as supplementary cementitious materials to replace Portland cement at 50 % by weight to produce a more environmentally friendly binder with a lower carbon footprint. Up to 30 % of calcined clay was used while calcareous fly ash was used at 20–50 %. Compressive strength and phase characterizations were investigated for these samples at 7 and 28 days to provide understandings of the phases formed during hydration. It is found that at both ages, the use of calcined clay in addition to fly ash resulted in an increase in the hydration phases as early as 7 days when compared to the reference fly ash mix and is more pronounced at 28 days. This relates with the increase in compressive strength of the mixes where the compressive strength of fly ash mixes with 15–20 % calcined clay are found to be ≈41 MPa compared to 29 MPa of reference fly ash mix (50 % fly ash). Using both thermogravimetric analysis (TG) and X-ray diffraction (XRD), a number of phases were detected such as calcium silicate hydrate (C-S-H), calcium aluminosilicate hydrate (C2ASH8) and monocarboaluminate hydrate. A noticeable reduction in calcium hydroxide (CH) was also clear when increasing calcined clay

Enrichment of Niobium and Titanium from Kaolin Using an Acid-Alkali Leaching Process

Niobium is a strategic resource because it is useful in a wide number of applications and its global distribution is uneven. It has been reported that kaolin clay from the bottom of the Xuanwei Formation, the Late Permian sequences in southwest China, contains Nb. In this paper, the major, trace, and mineral compositions of kaolin clay were characterized using XRF, ICP-MS, and XRD. The results show that it is mainly composed of kaolinite, anatase, and rutile, with a chemical composition of Al2O3 34.38pct, SiO2 39.97pct, TiO2 8.79pct, Fe2O3 3.24pct, and Nb 491g/g. A process including calcination treatment and acid-alkali leaching with HCl and NaOH was employed to separate Al, Fe, and Si in a leaching solution and to enrich Nb and Ti in the residue. The experimental results indicated that the reaction temperature played a vital role for Al and Fe extractions from acid leaching, while the concentration of alkali was the key factor for Si extraction. Under the optimal conditions, the contents of Nb and Ti in the final product were 4280g/g and 80.5pct, respectively