The efficacy of depuration using UV light and chlorinated seawater for decontaminating Vibrio parahaemolyticus and Vibrio vulnificus from oysters was investigated. Oysters were contaminated with a five-strain cocktail of V. parahaemolyticus or V. vulnificus to levels of 10(4) to 10(5) CFU ml(-1) for bioaccumulation. The depuration was conducted in a closed system in which 350 liters of seawater was recirculated at a rate of 7 liters/min for 48 h at room temperature. Counts of V. parahaemolyticus or V. vulnificus were determined at 0, 6, 18, 24, and 48 h. Three treatments were conducted: T1, control treatment; T2, UV treatment; and T3, UV plus chlorine treatment. After 48 h of depuration of V. parahaemolyticus, T3 reduced the count by 3.1 log most probable number (MPN) g(-1) and T2 reduced the count by 2.4 log MPN g(-1), while T1 reduced the count by only 2.0 log MPN g(-1). After 48 h of depuration of V. vulnificus, T2 and T3 were efficient, reducing the counts by 2.5 and 2.4 log MPN g(-1), respectively, while T1 reduced the count by only 1.4 log MPN g(-1). The UV light plus chlorine treatment was more efficient for controlling V. parahaemolyticus in oysters. Both UV light and UV light plus chlorine were efficient for V. vulnificus. The present study is the first report showing the efficacy of depuration systems for decontaminating V. parahaemolyticus and V. vulnificus in oysters cultivated on the Brazilian coast. This study provides information on processes that can contribute to controlling and preventing such microorganisms in oysters and could be used for effective postharvest treatment by restaurants and small producers of oysters on the coast of Brazil.

No abstract

No abstract

No abstract

The present study was conducted to define a methodology to produce and store small-scale microalgae paste to be used in a mollusk hatchery. Microalgae were cultured in 500 L fiberglass tanks, under temperature of 20 6 2 C, Guillard f/2 culture medium, and continuous light intensity of 203-226 mmol photons/m 2 /sec. Cultures were centrifuged at 2000 g at the exponential growth phase. Microalgae cell quality after centrifugation and during storage was determined by analyses with Evan's blue stain and by counting the number of total marine bacteria. Treatments with and without additive were applied to the microalgae paste produced, which was distributed into 100 mL plastic containers, capped, and stored under refrigeration at 4 6 1 C. Results indicated that in the Chaetoceros muelleri paste, centrifugation did not damage the cells and the number of total marine bacteria reduced significantly from 2.9 3 10 6 to 8.3 3 10 5 colony-forming units per milliliter. Chaetoceros muelleri and Chaetoceros calcitrans pastes stored with addition of 0.1% ascorbic acid had a shelf life shorter than 2 wk. For the treatment without additive, results with Evan's blue stain showed that cells (99%) remained viable until the sixth week of storage for C. muelleri and seventh week of storage for Skeletonema sp. and C. calcitrans. The number of bacteria did not increase during storage for C. calcitrans and Skeletonema (P . 0.05). For C. muelleri, an increase in bacteria (P , 0.05) was observed after the sixth week of storage. This study demonstrated the feasibility to produce and store microalgae paste for a period of 2-8 wk, which allows it to be used as food source and also optimizes the use of microalgae cultured in laboratory.