Continuous and recycling cultures were carried out with Aspergillus niger N402 wild-type and a glucoamylase overproducing transformant to investigate growth and product formation characteristics. In shake flask cultures, the amount of glucoamylase produced by the transformant was about five times more than by the wild-type strain. In contrast with these results, a twofold overproduction was found in glucose-limited continuous cultures, while no overproduction was found under maltodextin-limitation. Two regions of specific growth rates could be distinguished, one at specific growth rates lower (domain I) and one at specific growth rates higher than 0.12 h-' (domain 11). In domain I changes in mycelium morphology and conidia formation were observed. It has been concluded that maintenance requirements are dependent on the specific growth rate over the whole range of measured growth rates. The deviation in linearity in the linear equation of substrate utilization, caused by this phenomenon, should be considered when continuous cultures with filamentous fungi are performed. In recycling cultures, xylose as limiting carbon source repressed glucoamylase production very strongly. Under maltodextrinlimitation a fivefold overproduction was found. After about 150 h, the total amount of glucoamylase produced was still increasing, while total amount of product, measured as carbon, remained constant. After this time no increase in the amount of biomass formed was observed. These results suggest autolysis and cryptic growth taking place in a recycling fermenter and cell death rate equalling growth rate.
This study aims to develop a module based on discovery learning in improving scientific literacy skills in the 11th grade of science class in senior high school. This study refers to the modified Borg and Gall model into 7 steps, (1) preliminary study; (2) planning; (3) preparation of modules; (4) expert judgment; (5) revisions; (6) limited trials; (7) revision II. The research samples are in XI MIPA 2 and XI MIPA class at 3 SMAN 1 Bringin. The technique of collecting data using written tests, questionnaires, and observations. Hypothesis testing to measure the increase in cognitive learning outcomes of students using an independent t-test on n-gain students. Assessments from material experts, subject matter teachers, colleagues, and high school students show that the modules that have been developing suitable for use in the learning process with an achievement level of 86%, 95%, 88%, and 90% respectively. The results of the t-test showed an increase in students' literacy skills (p <0.05) of 0.71 (high category). It can be concluded, the modules that have been developing become worthy to use in the learning process and effective in enhancing the scientific literacy skills of senior high school students in XI class.
In Java, Indonesia, many nutrient-poor soils are intensively reforested with Pinus merkusii (pine). Information on nutrient cycles and microorganisms involved in these cycles will benefit the management of these important forests. Here, seasonal effects on the stratification of bacterial community structure in the soil profile of a tropical pine forest are described, and differences in bacterial communities are related to chemical and physical soil parameters. Culture-independent community profiles of litter, fragmented litter and mineral soil layers were made by denaturing gradient gel electrophoresis (DGGE) of 16S rDNA-specific polymerase chain reaction (PCR) fragments. The community profiles of the different soil layers clustered separately, correlating with significant differences in organic matter content between the three layers. The bacterial communities appeared to be stable during the wet season of 1998. The drought in 1997, caused by the El Niño climatic effect, did not influence the bacterial communities in fragmentation and mineral soil, although moisture content and other soil parameters were markedly lower than in the wet season. However, communities in litter were influenced by drought. In the litter layer, the moisture content was significantly lower than in the fragmentation and mineral layers during the dry season. A clone library was made from a litter sample taken during the wet season. Partial sequencing of 74 clones and linking the DGGE banding positions of these clones to bands in the DGGE profile of the sample from which the clone library was derived showed considerable bacterial diversity. Alpha-proteobacteria (40.5% of the clones, of which 57% belonged to the Rhizobium-Agrobacterium group) and high-G+C content, Gram-positive bacteria (36.5%) dominated the clone library.
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