Massey Documents by Type

Now showing 1 - 3 of 3

Raceway-based production of microalgae for possible use in making biodiesel : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biotechnology at Massey University, Palmerston North, New Zealand
(Massey University, 2014) Tahir, Sadia
Oils from microalgae are of interest as a potential feedstock for producing renewable transport fuels including gasoline, diesel, biodiesel and jet fuel. For producing feedstock oils, an alga must be capable of being grown easily in readily available seawater and have a high productivity of biomass and oil. This study explored the biomass and lipid production potential of the microalga Chlorella vulgaris in seawater media, as a potential producer of feedstock oils. The alga was grown photoautotrophically under various conditions in ~2 L Duran bottles and a pilot scale (~138 L) raceway system. Initially, eight species of microalgae of different classes were assessed under nutrient sufficient growth conditions for the production of biomass and lipids in ~2 L Duran bottles. Two of the promising species (C. vulgaris and Nannochloropsis salina) were then further evaluated extensively under various conditions (i.e. salinity stress, different levels of nitrogen in growth media, continuous light and light-dark cycling). Based on these assessments C. vulgaris stood out as the best alga for further detailed study. C. vulgaris was evaluated for biomass production and lipid production. The consumption rates of major nutrients (N and P) were quantified. Biomass was characterized for elemental composition and energy content at the end of the growth cycle. A maximum lipid productivity of ~31 mg L-1 d-1 was attained in Duran bottle batch culture under nitrogen starvation in continuous light with a lipid content in the biomass of 66% (dry weight). This appears to be the highest lipid content reported for C. vulgaris grown in seawater and demonstrates an excellent ability of this alga to accumulate high levels of oil. Under a 12:12 h light-dark cycle, the lipid content and productivity in Duran bottle batch culture were decreased by 13% and 41%, respectively, relative to the case for continuous illumination. Energy content of the biomass produced in Duran bottle batch culture exceeded 30 kJ g-1 both in continuous light and the 12: 12 h light-dark cycle. Batch and continuous culture kinetics of C. vulgaris in the raceway system were assessed. The alga was subjected to various light regimes and nitrogen starvation conditions. Although the N starvation enhanced the lipid accumulation by 42% relative to nutrient sufficient growth in batch culture, the highest biomass and oil productivities were attained under nutrient sufficient conditions in continuous mode of cultivation. Under nutrient sufficiency in continuous culture with a constant illumination of 91 μmol.m-2s-1, the productivities of biomass and lipid in the raceway were >61 mg L-1 d-1 and >8 mg L-1 d-1, respectively. This work represents the first detailed study of C. vulgaris in a raceway pond in full strength seawater media. Previous studies of this alga were almost always carried out in freshwater media.
Ethanolic fermentation of D-xylose and pine wood hydrolyzate by the yeast Pachysolen tannophilus : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biotechnology at Massey University
(Massey University, 1984) Wong, Tze Sen
This thesis reports a study of the ethanolic fermentation of D-xylose and wood hydrolyzate to ethanol by the yeast Pachysolen tannophilus with a view to developing an effective use of renewable hemi-cellulose hydrolysis products from New Zealand forest biomass residues. Initial work briefly addressed the problem of finding a suitable yeast from natural habitats suitable for the fermentation. Soon after that work commenced literature reports suggested that preliminary conversion of pentoses by enzymatic means was a possibility. Consequently, this aspect of conversion was considered and rejected. One reason for this was that literature was drawing attention to the pentose fermenting characteristics of Pachysolen tannophilus. Laboratory scale studies demonstrated the yeast Pachysolen tannophilus to be capable of fermenting the hexose and pentose sugars present in the hydrolyzate. The yeast's specific growth rate in the hydrolyzate could be improved by neutralizing the inhibitory substances with 2 g/l of anhydrous sodium sulphite. Ethanol has an inhibitory effect on growth but can also be readily assimilated by the yeast. Fermentation studied with gyration speeds of 50, 100 and 200 r.p.m. showed that oxygen was a critical parameter affecting growth and ethanol production. Batch fermentation experiments were pursued to examine this oxygen phenomenon more closely. Cell growth, substrate uptake rate and culture pH responded strongly to the supply of oxygen. However, production of ethanol accompanied cell growth only in late "exponential" phase. Fermentation characteristics were established under continuous culture at an aeration rate of 0.37 l/l.min and values obtained were as follows; maximum specific growth rate, 0.046 h-1; biomass yield, 0.04 g/g; ethanol yield, 0.17 g/g; Ks value, 13 g/l and Ki values, 0.5 g/l. A redox potential controlled chemostat study revealed that steady-state culture poised at -50 mV exhibited a 55% increased ethanol concentration and 43% decreased xylitol concentration over the value observed without redox control. With a knowledge or D-xylose fermentation as established in these batch and chemostat experiments, it was possible to consider more detailed aspects of the fermentation which would be applicable to process development. Questions addressed included which strain of Pachysolen tannophilus should be used, what quantity of inoculum was necessary, what interactions existed between fermentation variables. Statistically designed experiments were employed to answer these questions. Empirical models so developed revealed that ethanol yield has a linear relationship with initial substrate concentration. These models have given some insight into how environmental factors affect the ethanolic fermentation by this yeast and have also indicated the optimal conditions required for an effective fermentation of wood pentoses. These important fermentation process variables were established and are expected to be useful in moving the process from laboratory scale as carried out here to a pilot plant scale of operations. The values established were temperature, 28° or lower; initial medium pH for ethanol production, 5.6 to 5.8; substrate concentration used can be up to 80 g/l of pentoses; minimum inoculum density, 5.5 g/l dry weight cells and NRRL Y-2461 was recommended as the best strain to achieve the fermentation. The pre-treatment of the prehydrolyzate by 2 g/l of anhydrous sodium sulphite was highly desirable in order to enhance growth and fermentation rates. The research has shown that Pachysolen tannophilus is capable of fermenting pentose fraction of wood hydrolyzate and that the optimal conditions for this fermentation will lead to significant utilization of wood sugar. However, in the completely mixed reactor systems used in these experiments, the ethanol yields obtained were not as attractive as those observed for hexose fermentations under similar conditions. This, it is felt, points to the greater difficulty the yeast experiences in fermenting pentoses and it also suggests the need to investigate the value of other reactor formats at seme future date.
The Extraction Of Gold From Plants And Its Application To Phytomining
(Massey University., 2001-09-01) Lamb, A. E.; Anderson, C. W. N.; Haverkamp, Richard G.
Phytomining is the use of hyperaccumulating plants to extract a metal from soil with recovery of the metal from the biomass to return an economic profit. This work looks at the possible methods for recovering gold from plant material, including chemical reduction with and without solvent extraction, thermal reduction and copper electrodeposition. Some progress was made with ascorbic acid as the chemical reductant. A solid phase was produced at the liquid-liquid interface after solvent extraction. The deposition reaction reduced the gold concentration in methyl isobutyl ketone (MIBK) to less than 2 ppm, equating to 85% recovery, in 3.5 hours. Copper electrodeposition also gave some promising results. However, both require much more work before they are viable for scale-up.

Massey Documents by Type

Browse

Filters

Settings

Sort By

Results per page

Search Results