Publications by authors named "Craig J Oberg"
The genus Lactobacillus has represented an extremely large and diverse collection of bacteria that populate a wide range of habitats, and which may have industrial applications. Researchers have grappled with the immense genetic, metabolic, and ecological diversity within the genus Lactobacillus for many years. As a result, the taxonomy of lactobacilli has been extensively revised, incorporating new genus names for many lactobacilli based on their characteristics including genomic similarities.
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- The study compares the growth and survival of four strains of bacteria (two L. lactis and two L. cremoris) used as starter cultures in Cheddar cheese production, focusing on how they perform during cheesemaking and post-salting.
- A standardized cheesemaking procedure was followed, and various salt levels were tested, revealing that bacterial growth was much higher in L. lactis strains compared to L. cremoris strains.
- Flow cytometry showed about 5% of starter cells were dead after 6 days of storage, while some cells were alive but semipermeable, with L. cremoris strains having a higher proportion of these semipermeable cells.
Article Synopsis
- The study focuses on the gas production issues caused by a type of bacteria called Paucilactobacillus wasatchensis in Cheddar cheese, which can lead to undesirable slits and cracks.
- The researchers aimed to create a model test to analyze how the bacteria utilized galactose and ribose and whether other bacteria could prevent gas formation.
- Findings showed that co-inoculating Pa. wasatchensis with certain galactose-fermenting bacteria significantly reduced gas production by depleting galactose, indicating a potential method for mitigating gas issues in cheese.
Understanding characteristics that permit survival and growth of Paucilactobacillus wasatchensis as part of the nonstarter microbiota of cheese is important for minimizing unwanted gas formation in cheese that can cause downgrading because of slits and cracks. The ability of Plb. wasatchensis WDC04 to survive pasteurization was studied by inoculating raw milk with 10 cfu/mL and measuring survival after processing through a high-temperature, short-time pasteurizer.
View Article and Find Full Text PDFLactobacillus wasatchensis, an obligate heterofermentative nonstarter lactic acid bacteria (NSLAB) implicated in causing gas defects in aged cheeses, was originally isolated from an aged Cheddar produced in Logan, Utah. To determine the geographical distribution of this organism, we isolated slow-growing NSLAB from cheeses collected in different regions of the United States, Australia, New Zealand, and Ireland. Seven of the cheeses showed significant gas defects and 12 did not.
View Article and Find Full Text PDFA Gram-stain positive, rod-shaped, non-spore-forming strain (WDC04T), which may be associated with late gas production in cheese, was isolated from aged Cheddar cheese following incubation on MRS agar (pH 5.2) at 6 °C for 35 days. Strain WDC04T had 97 % 16S rRNA gene sequence similarity with Lactobacillus hokkaidonensis DSM 26202T, Lactobacillus oligofermentans 533, 'Lactobacillus danicus' 9M3, Lactobacillus suebicus CCUG 32233T and Lactobacillus vaccinostercus DSM 20634T.
View Article and Find Full Text PDFA novel slow-growing, obligatory heterofermentative, nonstarter lactic acid bacterium (NSLAB), Lactobacillus wasatchensis WDC04, was studied for growth and gas production in Cheddar-style cheese made using Streptococcus thermophilus as the starter culture. Cheesemaking trials were conducted using S. thermophilus alone or in combination with Lb.
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- The study investigates the performance of a newly identified bacterium, Lactobacillus wasatchensis, in Cheddar cheese, comparing its growth and gas production in regular cheese and those supplemented with specific sugars (ribose and galactose) at varying temperatures.
- Initial results showed that starter culture counts decreased significantly in control cheese, while Lb. wasatchensis could grow well in supplemented cheeses, particularly under warmer ripening conditions (12°C).
- The addition of ribose and galactose enhanced gas production, especially at 12°C, suggesting that Lb. wasatchensis efficiently used these sugars for growth and gas formation during the ripening process.
Article Synopsis
- Researchers studied a new type of lactic acid bacterium, Lactobacillus wasatchii, isolated from gassy Cheddar cheese, focusing on its growth, gas production, salt tolerance, and survival through pasteurization at specific temperatures.
- Initially believed to only use ribose for energy, experiments showed that Lb. wasatchii also utilizes galactose, particularly thriving at 23°C when both sugars are present, leading to higher growth rates than when only galactose is used.
- The bacterium likely uses ribose for energy while employing galactose for essential functions like cell wall synthesis, showing an adaptation to effectively ferment sugars in the cheese environment.
Halophage CW02 infects a Salinivibrio costicola-like bacterium, SA50, isolated from the Great Salt Lake. Following isolation, cultivation, and purification, CW02 was characterized by DNA sequencing, mass spectrometry, and electron microscopy. A conserved module of structural genes places CW02 in the T7 supergroup, members of which are found in diverse aquatic environments, including marine and freshwater ecosystems.
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- The study investigated how different fat contents (0%, 11%, and 19%) and coagulant levels (0.25X, 1X, and 4X) affected the properties of mozzarella cheese over 60 days of storage at 5°C.
- Results showed that lower fat content cheese had slower rates of proteolysis and less moisture, affecting their functional properties.
- Cheese softness and meltability improved with higher fat and coagulant levels, while nonfat cheese showed minimal change during storage.