The genes coding for the expression of a ropy exopolysaccharide responsible for commercially desirable textural and rhealogical traits in fermented milk products by a natural lactococcal ropy isolate were sought. Using a transposon mutagenesis vector, pGh9:ISS1, three mutants lacking expression of the ropy exopolysaccharide were isolated. One of the mutants was chosen for further characterization. Using a Southern hybridization analysis, the interrupted gene was localized to the chromosome. The non-ropy mutant was further characterized and shown to be unable to produce ropy exopolysaccharide in fermented milk. A 2006 by fragment of the interrupted gene was sequenced. The DNA sequence over a short region showed homology to sugar transfer enzymes found in exopolysaccharide biosynthesis pathways. The DNA sequence was translated into its predicted amino acid sequences and two partial open reading frames of 236 and 338 amino acid residues in length were identified. These open reading frames were found to exhibit identity to glycosyltransferases present in exopolysaccharide biosynthesis pathways in other bacteria. / Graduation date: 1999

No description available.

The conversion of soybeans to tempe is achieved through fermentation by Rhizopus. This fermentation process leads to hydrolysis of both proteins and lipids. The present work investigated certain biochemical changes which accompany the conversion of soybeans to tempe. The contents of non-protein nitrogen and free $ alpha$-amino nitrogen increased from 2.34 to 15.14%, and 2.03 to 5.22%, respectively after 48 h fermentation. SDS electrophoresis showed that a substantial quantity of the proteins in raw soybeans were hydrolysed by the Rhizopus to low molecular species (molecular weight $<$13,000 Daltons). Trypsin inhibitor activity found in tempe was lower than that of soybean and soaked soybean (an intermediate step in tempe preparation). The protein digestibilities of tempe and soaked soybean were higher than that of soybean. Reversed phase HPLC showed that the peptide separation profile of tempe was different from that of soybean and soaked soybean. The ESI/MS of the RP-HPLC fractions gave molecular weight of soybean peptides ranging from 1962 Da to 22,699 Da and tempe peptides ranging from 569 Da to 16,688 Da. The fatty acid compositions of tempe, soybean and soaked soybean were similar; relatively high levels of linoleic acid followed by oleic, linolenic and stearic acids were found. The acid values increased from 1.49 to 11.42 during the fermentation of soybeans. The total soluble carbohydrate contents of soybean, tempe and soaked soybean as well as the types and quantities of individual sugars were similar. The fermentation of soybean by Rhizopus had only a minor effect on the proximate composition of soybean; however, the soybean and fungal enzymes contributed primarily to changes in protein composition.

Thesis (Ph. D.)--Victoria University (Melbourne, Vic.), 2007. / Includes bibliographical references.

No description available.

No description available.

Parasitological and selected microbiological safety aspects of Nham (Thai-style fermented pork sausage) were evaluated. Pork meat from pigs experimentally infected with Trichinella spiralis was divided into 4 portions; 3 portions were frozen at -23°C for 12, 18 and 24 hours before they were made into Nham. The formula for fermented sausage included 3% w/w NaCl and garlic, 0.015% each of NaN0₂ and NaNO₃, and either 1.0 or 1.5% w/w commercial starter culture. Fermentation was at 30°C for 96 hours. The higher level of starter culture resulted in faster acid production but no difference in the maximum number of lactic acid bacteria attained. Infected pork, after being frozen for 24 hours, was still found to cause a low level of parasitism. However, the corresponding fermented samples were noninfective. Use of 1.0% starter culture and 12 hours freezing of meat prior to grinding rendered trichinae larvae noninfective after 2 days of sausage fermentation. Staphylococcus aureus (10³ cells per g) and Escherichia coli (10⁴ cells per g) were introduced into the ground pork in a series of experiments. Starter culture levels used were 0.75% and 1.5% by weight. Fermentation without starter culture stabilized the numbers of E. coli but permitted slow multiplication of S. aureus. Adding starter culture at either level increased the rate of acid production during the initial days, resulting in a faster drop in pH and a decline in numbers of both S. aureus and E. coli. After 36 and 48 hours, viable S. aureus were not recovered from products with 1.5% and 0.75% starter culture, respectively. E. coli disappeared from sausages with 1.5% starter culture after 96 hours but persisted at low numbers when the lower level of starter culture was used. The rapid direct plating technique (RPT) for enumeration of E. coli was compared to the two standard methods generally used: plating on Violet Red Bile Agar (VRBA) and Host Probable Number (MPN). Total coliforms from 43 fermented pork sausages were enumerated. The RPT gave data highly correlated to those from VRBA but with a significantly lower correlation to MPN. The regression line of loglO coliform counts from the RPT and VRBA had a slope of 0.76 and an intercept of 0.98. The MPN assay gave significantly higher (P=0.05) numbers than either the VRBA or the RPT. / Graduation date: 1986

No description available.

No description available.

No description available.