Anaerobic Fish Spoilage by Bacteria I. Biochemical Changes in Herring Extracts

Abstract

Water extracts of herring fillets were used as laboratory model substrates for the study of anaerobic bacterial spoilage of fish stored in bulk. The organisms studied (Enterobacter sp., str. NTHC 151, Proteus sp., str. NTHC 153, and Aeromonas sp., str. NTHC 154) were selected for by an enrichment method designed to isolate the bacteria having the highest anaerobic growth yields in these herring extracts. The extracts were then inoculated with pure cultures of the bacteria and incubated anaerobically at 15°C. Chemical analyses of the extracts were carried out at the start and at the end of the incubation period. The compounds determined accounted for 88% of total carbon and 93% of total nitrogen of the sterile extracts. Ribose (free and bound), free hexoses and lactate were the main substrates for the growth of the bacteria. These compounds were converted to acetate and CO2; hydrogen liberated by these processes was used for the quantitative reduction of trimethylamine oxide to trimethylamine. Fermentation balances support the contention that the biochemical changes observed represent the quantitative dominating chemical events in the herring extracts as a result of the development of the spoilage bacteria.

Amino acid and lactate catabolism in trimethylamine oxide respiration of Alteromonas putrefaciens NCMB 1735

“…To prevent inhibition of growth by increased pH due to the high TMA production, pH was kept constant at 7.5 in all growth experiments by addition of HCl. This pH problem is less pronounced when TMAO respiration in enteric bacteria is studied, because the ratio between TMAO reduction and substrate conversion is much lower (30,31). Furthermore, the finding that a variety of amino acids served as substrate during TMAO-dependent anaerobic growth of A. putrefaciens bears resemblance to the process of nitrate respiration in a nonfermentative pseudomonad (22); whereas in the fermentative enteric bacteria, a limited number of amino acids, often only serine, serve as energy source during nitrate (14) and TMAO (30) respiration.…”

New Method for Evaluating Bacterial Reduction of Trimethylamine N‐oxide and Its Application to Bacterial Populations in Fish Muscle

“…principally Acinetobacter, Pseudomonas, Alteromonus. Vibrio, Corynebacter (Easter et al 1982;Laycock and Regier 1971;Lerke et al 1965: Watson 1939, but also by Enterobacteria such as Proreus, Escherichia coli, Aerobacter, and more rarely by certain pathogenic strains such as Salmonella and Shigella (Strom and Larsen 1979;Tarr 1940;Wood and Baird 1943), as well as by some Flavobacteria (Castell and Mapplebeck 1952). A relation has been established between the growth of bacterial flora and the quantity of TMAO reduced to TMA (Lundstrom and Racicot 1983).…”

“…TMAO reduction under anaerobic conditions by Proreus spp. (Strom and Larsen 1979). Escherichia coli (Ishirnoto and Shimokawa 1978) and Shewanella putrefaciens Stenberg et al 1984) may be activated by glucose, pyruvate, lactate, formate, glutamate.…”

“…Lcysteine, serine and NaCl. TMAO is a natural proton acceptor (Strom and Larsen 1979) which also stimulates the growth under anaerobic conditions of Salmonella ryphimurium (Kim and Chang 1974). Escherichia coli (Yamamoto and Ishimoto 1977), and Shewanella purrefaciens .…”

The expression of proteinases and haemolysins byAeromonas hydrophilaunder modified atmospheres

“…There are reports con®rming that Aer. hydrophila synthesize and express active extracellular proteinases in the absence of oxygen (Strùm and Larsen 1979;Fyfe et al 1986). Thus, oxygen is not a prerequisite for aeromonad extracellular proteinase expression.…”