Kelp waste extracts combined with acetate enhances the biofuel characteristics of Chlorella sorokiniana

Reducing culture medium nitrogen supply coupled with replenishing carbon nutrient simultaneously enhances the biomass and lipid production of Chlamydomonas reinhardtii

Chlamydomonas reinhardtii is a model strain to explore algal lipid metabolism mechanism, and exhibits great potentials in large-scale production of lipids. Completely lacking nitrogen is an efficient strategy to trigger the lipid synthesis in microalgal cells, while it always leads to the obvious reduction in the biomass. To illustrate the optimal culture substrate carbon (C) and nitrogen (N) levels to simultaneously stimulate the growth and lipid production of C. reinhardtii, cells were cultivated under altered C and N concentrations. Results showed that replenishing 6 g/L sodium acetate (NaAc) could increase 1.50 and 1.53 times biomass and lipid productivity compared with 0 g/L NaAc treatment (the control), but total lipid content slightly decreased. Reducing 75% of basic medium (TAP) N level (0 g/L NaAc + 0.09 g/L NH₄Cl treatment) could promote 21.57% total lipid content in comparison with the control (containing 0.38 g/L NH₄Cl), but decrease 44.45% biomass and 34.15% lipid productivity. The result of the central composite design (CCD) experiment suggested the optimum total lipid content together with higher biomass and lipid productivity could be obtained under the condition of 4.12 g/L NaAc and 0.20 g/L NH₄Cl. They reached 32.14%, 1.68 g/L and 108.21 mg/L/d, and increased by 36.77%, 93.10% and 1.75 times compared with the control, respectively. It suggests moderately increasing C supply and decreasing N levels could synchronously improve the biomass and lipid content of C. reinhardtii.

Bioremediation of Pyropia-processing wastewater coupled with lipid production using Chlorella sp

Pyropia-processing wastewater (PPW) contains diverse organic nutrients and causes environmental pollution. To explore the nutrient removal efficiency and growth performance of Chlorella sp. on PPW, the cultures were conducted in different culture substrates. Results showed that, after 7 days of incubation, the removal rates of total nitrogen (TN), total phosphorus (TP) and phycobiliprotein (PP) all reached more than 90% by cultivating Chlorella sp. C2 and C. sorokiniana F-275 in PPW. The chemical oxygen demand (COD) removal efficiencies could be over 50%. Meanwhile, the increments of biomass in two tested Chlorella strains were 1.39 and 4.89 times higher than those of BG11 and BBM substrates and the increases in lipid productivity were 1.34 and 10.18- fold, respectively. The C18:3 fatty acid proportions were markedly reduced by 27.89% and 29.10%. These results suggest that Chlorella sp. could efficiently reduce various nutrients in PPW and simultaneously accumulate higher biomass with higher biodiesel characteristics.

Utilization of tannery wastewater for biofuel production: New insights on microalgae growth and biomass production

Microalgae cultivation on tannery wastewater (TWW) has been examined in some studies as a possible biological application to reduce contamination load and discharge effluents safely. However, Growth aspects, different tolerate strains and enriching the medium were not well investigated. In our study we applied Scenedesmus sp., Chlorella variabilis and Chlorella sorokiniana with different TWW concentrations. C. sorokiniana and C. variabilis cell density, chlorophyll, and sugar content grew substantially as compared to control. C. sorokiniana biomass and total lipids folded three and two times in 25% and 40% TWW, respectively as compared to control. Scenedesmus sp. showed longer lag phase and lower performance compared to the other two strains. Kelp waste extract (KWE) was added to balance the nutrients supply for C. sorokiniana, of which growth and effluents indicators were then greatly promoted in all concentrations. As the lag phase was shortened from 8 to 4 days in 60% concentration, subsequently, chlorophyll, carbohydrates, biomass and total lipids appreciated by 184%, 400%, 162% and 135%, respectively. Furthermore, the COD and ammonium removals improved by 51% and 45%, respectively. These outcomes emphasize the suitability of using TWW for microalgae cultivation with the suitable concentration while adding kelp waste extract for further enhancement.

Using agro-industrial wastes for mixotrophic growth and lipids production by the green microalga Chlorella sorokiniana

There has been growing interest in the use of microalgae for the production of biofuels, but production costs continue to be too high to compete with fossil fuel prices. One of the main limitations for photobioreactor productivity is light shielding, especially at high cell densities. The growth of the green microalga Chlorella sorokiniana, a robust industrial species, has been evaluated under different trophic conditions with traditional carbon sources, such as glucose and sucrose, and alternative low cost carbon sources, such as carob pod extract, industrial glycerol and acetate-rich oxidized wine waste lees. The mixotrophic cultivation of this microalga with wine waste lees alleviated the problems of light shielding observed in photoautotrophic cultures, improving specific growth rate (0.052 h^-1) compared with the other organic sources. The fed-batch mixotrophic culture of Chlorella sorokiniana in a 2 L stirred tank reactor, with optimized nutritional conditions, 100 mM of acetate coming from the oxidized wine waste lees and 30 mM of ammonium, produced an algal biomass concentration of 11 g L^-1 with a lipid content of 38 % (w/w). This fed-batch strategy has been found to be a very effective means to enhance the biomass and neutral lipid productivity.

Extraction, isolation and characterization of nanocrystalline cellulose from industrial kelp (Laminaria japonica) waste

Kelp (Laminaria japonica) is an economically important type of algae cultured in East Asia. Kelp waste is a by-product from the extraction of commercial alginate from kelp. This work reports the isolation of nanocrystalline cellulose (NCC) from the cellulose extracted from the kelp waste. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) show that the crystallinity index of the isolated kelp NCC was 69.4%, which was slightly higher than that of kelp cellulose as well as maintained the cellulose I crystalline form and typical cellulose chemical structure. In thermogravimetric analysis (TGA), kelp NCC showed decreased thermostability and a higher residual mass. Transmission electronic microscopy (TEM) confirmed the ordinary rod-like shape of the produced NCC with various dimensions. The kelp NCC aqueous dispersions displayed the expected characteristic optical and gel effects. Studies on the variables and the orthogonal experiment of NCC preparation contributed a maximum yield of 52.3%. The exploration on the preparation of kelp NCC in this study lays foundations for future applications.