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There were two primary goals in this investigation. The first goal was to determine if inter-individual variability in time to exhaustion at the velocity associated with V02max (Tlim at Vmax) was explained by anaerobic capacity (AC), Vmax, anaerobic threshold (AT), and/or a combination variable in the form [AC • (Vmax - vAT)^-1]. The second goal was to determine if AC could be predicted from Tlim at Vmax, AT, and/or a combination variable in the form [Tlim • (Vmax - vAT)].

Thesis (M.S.)--University of Michigan, 1985.

Thesis (M.S.)--University of Michigan, 1985.

Orientador: Eduardo Kokubun / Banca: Claudio Alexandre Gobatto / Banca: Vilmar Baldissera / Resumo: Conhecimentos sobre a participação dos metabolismos aeróbio e anaeróbio em exercício são importantes para compreender e prever os efeitos dos diferentes tipos de treinamentos. Muitos modelos têm sido propostos para a predição da participação dessas duas vias energéticas no exercício. Um deles, proposto em 1965, sugere a existência de uma intensidade de esforço, denominada potência crítica (PC), abaixo da qual o suprimento energético é dependente exclusivamente do metabolismo aeróbio. Até a intensidade da PC, o exercício pode ser realizado por longo tempo, sem exaustão. Acima dessa intensidade, as reservas anaeróbias de energia de dimensão finita denominada capacidade de trabalho anaeróbio (CTA), são requeridas e sua total depleção está associada com a exaustão. A aplicabilidade deste modelo vem sendo estudada e comprovada em exercícios contínuos, constituindo uma forma simples e não invasiva de se determinar as capacidades aeróbia e anaeróbia. O propósito deste estudo foi explorar o exercício intermitente através do modelo da potência crítica, principalmente quanto aos efeitos da duração da pausa na reposição da CTA. Indivíduos ativos foram submetidos a exercícios contínuos e intermitentes realizados em cicloergômetro, até a exaustão. Para os testes intermitentes, os regimes de esforço-pausa foram 15 s de exercício por 15 s, 30 s, 45 s e 60 s de pausa passiva. A PC e CTA foram determinadas a partir dos testes contínuos, através de regressão linear simples, segundo a equação P = CTA x 1/tlim + PC. A comparação entre as variáveis foi realizada através da análise de variância (ANOVA) para medidas repetidas, com nível de significância de 5% (p<0,05). Os principais resultados indicam que: da quantidade total de trabalho intermitente realizado, aproximadamente 58%, 85%, 88% e 90% correspondeu ao... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The knowledge of the contribution of aerobic and anaerobic metabolism during exercises plays a key role to anticipate the effects of different types of training. Many models have been proposed to predict the contribution of these two energetic pathways on the exercise work output. Among them, a model, proposed by Monod and Scherrer in 1965, suggests the existence of an exercise's intensity, named critical power (CP), below which the energetic supply is dependent, exclusively, on the aerobic metabolism. At the intensity corresponding to or below the critical power, the exercise can be done for a long time without exhaustion. Above this intensity, the finite anaerobic reserves of energy named anaerobic work capacity (AWC) are required and its total depletion is associated with exhaustion. The applicability of this model has been studied and confirmed in continuous exercises. It has been recognized as a simple and not invasive procedure to determine aerobic and anaerobic capacities. The purpose of this study was to explore the intermittent exercise through the critical power model, specifically the effects of the pause's duration on the replacement of the AWC. Active subjects were submitted to a continuous and intermittent ciclergometer exercises until exhaustion. For the intermittent tests, the exercise rest regimes were 15 s of exercise and 15 s, 30 s, 45 s and 60 s of passive recovery. The CP and AWC were determined by the results of continuous tests through a simple linear equation: P = AWC x 1/tlim + CP. The comparison among the variables was done by the analysis of variance (ANOVA) for repeated measures with a significance level of 5% (p<0,05). The main results indicated that: 1) from the total amount of intermittent work, approximately 58%, 85%, 88% and 90% was extra when compared to the continuous exercise for the same time of tests with 15 s, 30... (Complete abstract, click electronic address below) / Mestre

Endoglucanases play an important function in cellulose hydrolysis and catalyse the initial attack on the polymer by randomly hydrolysing the β-1,4 glucosidic bonds within the amorphous regions of cellulose chains. Cellulolytic bacteria have been isolated and characterised from the sewage sludge and the activation of several hydrolytic enzymes under biosulphidogenic conditions of sewage hydrolysis has been reported. The aims of this study were to: identify, induce production, locate and isolate, characterise (physicochemical and kinetic) and purify endoglucanases from anaerobic biosulphidogenic sludge. The endoglucanase activities were shown to be associated with the pellet particulate matter and exhibited a pH optimum of 6 and temperature optimum of 50 °C. The enzymes were thermally more stable when immobilised to the floc matrix of the sludge than when they were released into the aqueous solution via sonication. For both immobilised and released enzymes, sulphate was slightly inhibitory; activity was reduced to 84 % and 77.5 % of the initial activity at sulphate concentrations between 200 and 1000 mg/l, respectively. Sulphite was stimulatory to the immobilised enzymes between 200 and 1000 mg/l. Sulphide stimulated the activities of the immobilised endoglucanases, but inhibited activities of the soluble enzymes above 200 mg/l. The enzyme fraction did not hydrolyse avicel (a crystalline substrate), indicating the absence of any exocellulase activity. For CMC (carboxymethylcellulose) and HEC (hydroxylethylcellulose) the enzyme had K_m,app_ values of 4 and 5.1 mg/ml respectively and V_max,app_ values of 0.297 and 0.185 μmol/min/ml respectively. Divalent ions (Cu²⁺, Ni²⁺ and Zn²⁺) proved to be inhibitory while Fe²⁺, Mg²⁺ and Ca²⁺ stimulated the enzyme at concentrations between 200 and 1000 mg/l. All the volatile fatty acids studied (acetic acid, butyric acid, propionic acid and valeric acid) inhibited the enzymes, with acetic acid eliciting the highest degree of inhibition. Sonication released ~74.9 % of the total enzyme activities into solution and this was partially purified by PEG 20 000 concentration followed by DEAE-Cellulose ion exchange chromatography, which resulted in an appreciable purity as measured by the purification factor, 25.4 fold.

Acidogenic codigestion of fats, oils, and greases (FOG) was studied at 37"C using suspended sludge digesters operated as sequencing batch reactors (SBRs). Volatile fatty acid (VFA) production was found to increase with larger FOG loading rates, although this increase was insignificant compared the theoretical VFA production from FOG addition. Long chain fatty acids (LCFAs) were found to have accumulated in the reactor vessel in semi-solid balls that were primarily composed of saturated LCFAs. Adding high FOG loadings to an APD not acclimated to LCFAs allowed for a mass balance calculation and resulted in near complete saturation of unsaturated LCFAs and significant accumulation of LCFA material in the digester, which was found to be mostly 16:0, 18:0, and 18:1. While 18:2 and 18:3 LCFAs were nearly completely removed, 18:0 and 14:0 LCFAs were produced, most likely from the degradation of 18:2 and 18:3 LCFAs. The APD pH was found to have a significant impact on the amount of accumulated LCFA material present, with higher pH levels resulting in less accumulated material. Two-phase codigestion of FOG was also studied using an APD followed by gas-phase (GPD) digesters. The two-phase systems were compared by FOG addition to the APD versus GPD. FOG addition to the APD resulted in 88% destruction of LCFAs, whereas FOG addition to the GPD resulted in 95% destruction of LCFAs. Accumulated LCFAs in the APD receiving FOG were composed mostly of stearic acid (18:0). The low pH of the APD is likely the cause of LCFA accumulation due to saturation of unsaturated LCFAs. / Master of Science

LD2668 .T4 1962 R63

Pacific Island Countries (PICs) currently rely heavily on imported, expensive and unsustainable fossil fuels as their primary source for energy production. Establishing an alternative energy source from local resources would therefore have considerable benefits for many Island communities. Coconut copra is high in biodegradable organic carbon and is found growing abundantly in PICs. One alternative use for this local resource would potentially be the conversion of the coconut copra into a valuable and useful energy source through biological processes, such as anaerobic digestion. The purpose of this research was to investigate the biogas generation potential of coconut copra as a carbon source using anaerobic digestion processes. Both batch and continuously stirred reactors (CSTRs) in addition to the environmental and operating variables that affect the production of biogas were investigated in order to optimize methane production and increase the overall conversion efficiencies of organic matter to methane. The results suggest that coconut copra is amenable to anaerobic digestion due to the high theoretical methane yields from the substrate’s high lipid content. However, the optimal organic loading rate (OLR) was limited to within a narrow range of 3.6-6 g VS (2.4 - 4 g VS/L Reactor) for the batch reactors and a maximum of 0.420 L CH4/ g VS was achieved at an OLR of 3.6 g VS. OLRs exceeding 15 g VS resulted in low pH values and negligible methane production due to substrate overloading. High average methane yields of 0.708 L CH4/ g VS•day were also successfully achieved for the CSTRs and increased mixing was observed to have an improved effect on methane production. However, the addition of nitrogen and phosphorus supplements failed to increase biological activity and ultimately resulted in the accumulation of ammonia to concentrations toxic to methanogenic bacteria. The failure of an accelerated CSTR start-up procedure also reinforced the requirement for a gradual and steady acclimated period for anaerobic digestion of this particular substrate.

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