Inorganic salt starvation improves the polysaccharide production and CO2 fixation by Porphyridium purpureum.

The microalgae industry shows a promising future in the production of high-value products such as pigments, phycoerythrin, polyunsaturated fatty acids, and polysaccharides. It was found that polysaccharides have high biomedical value (such as antiviral, antibacterial, antitumor, antioxidative) and industrial application prospects (such as antioxidants). This study aimed to improve the polysaccharides accumulation of Porphyridium purpureum CoE1, which was effectuated by inorganic salt starvation strategy whilst supplying rich carbon dioxide. At a culturing temperature of 25 °C, the highest polysaccharide content (2.89 g/L) was achieved in 50% artificial seawater on the 12th day. This accounted for approximately 37.29% of the dry biomass, signifying a 25.3% increase in polysaccharide production compared to the culture in 100% artificial seawater. Subsequently, separation, purification and characterization of polysaccharides produced were conducted. Furthermore, the assessment of CO2 fixation capacity during the cultivation of P. purpureum CoE1 was conducted in a 10 L photobioreactor. This indicated that the strain exhibited an excellent CO2 fixation capacity of 1.66 g CO2/g biomass/d. This study proposed an efficient and feasible approach that not only increasing the yield of polysaccharides by P. purpureum CoE1, but also fixing CO2 with a high rate, which showed great potential in the microalgae industry and Bio-Energy with Carbon Capture and Storage.

Cellulase production and efficient saccharification of biomass by a new mutant Trichoderma afroharzianum MEA-12.

BACKGROUND: Cellulase plays a key role in converting cellulosic biomass into fermentable sugar to produce chemicals and fuels, which is generally produced by filamentous fungi. However, most of the filamentous fungi obtained by natural breeding have low secretory capacity in cellulase production, which are far from meeting the requirements of industrial production. Random mutagenesis combined with adaptive laboratory evolution (ALE) strategy is an effective method to increase the production of fungal enzymes. RESULTS: This study obtained a mutant of Trichoderma afroharzianum by exposures to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), Ethyl Methanesulfonate (EMS), Atmospheric and Room Temperature Plasma (ARTP) and ALE with high sugar stress. The T. afroharzianum mutant MEA-12 produced 0.60, 5.47, 0.31 and 2.17 IU/mL FPase, CMCase, pNPCase and pNPGase, respectively. These levels were 4.33, 6.37, 4.92 and 4.15 times higher than those of the parental strain, respectively. Also, it was found that T. afroharzianum had the same carbon catabolite repression (CCR) effect as other Trichoderma in liquid submerged fermentation. In contrast, the mutant MEA-12 can tolerate the inhibition of glucose (up to 20 mM) without affecting enzyme production under inducing conditions. Interestingly, crude enzyme from MEA-12 showed high enzymatic hydrolysis efficiency against three different biomasses (cornstalk, bamboo and reed), when combined with cellulase from T. reesei Rut-C30. In addition, the factors that improved cellulase production by MEA-12 were clarified. CONCLUSIONS: Overall, compound mutagenesis combined with ALE effectively increased the production of fungal cellulase. A super-producing mutant MEA-12 was obtained, and its cellulase could hydrolyze common biomasses efficiently, in combination with enzymes derived from model strain T. reesei, which provides a new choice for processing of bioresources in the future.

Correction to: Induced cultivation pattern enhanced the phycoerythrin production in red alga Porphyridium purpureum.

The original version of the article unfortunately contained an error in Microalgae strain and culture medium section. Below is the corrected version.

Induced cultivation pattern enhanced the phycoerythrin production in red alga Porphyridium purpureum.

Porphyridium purpureum is a rich source for producing phycoerythrin (PE); however, the PE content is greatly affected by culture conditions. Researchers have aimed to optimize the cultivation of P. purpureum for accumulation of PE. When traditional optimized culture conditions were used to cultivate P. purpureum, high PE contents were not usually achieved. In this study, an induced cultivation pattern was applied to P. purpureum for PE biosynthesis (i.e., an incremental approach by altering temperatures, light intensities, and nitrate concentrations). Results revealed that the induced pattern greatly improved the PE biosynthesis. The optimized PE content of 229 mg/L was achieved on the 12th cultivation day, which was a maximum PE content within one cultivation period and accounted for approximately 3.05% of the dry biomass. The induced cultivation pattern was highly suitable for PE synthesis in P. purpureum, which provided an important reference value to the large-scale production of PE.