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Boletus edulis Nitrite Reductase Reduces Nitrite Content of Pickles and Mitigates Intoxication in Nitrite-intoxicated Mice.

Zhang W, Tian G, Feng S, Wong JH, Zhao Y, Chen X, Wang H, Ng TB - Sci Rep (2015)

Bottom Line: Pickles are popular in China and exhibits health-promoting effects.The optimum temperature and pH of the enzyme was 45 °C and 6.8, respectively.B. edulis NiR was capable of prolonging the lifespan of nitrite-intoxicated mice, indicating that it had the action of an antidote.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory for Agrobiotechnology and Department of Microbiology, China Agricultural University, Beijing 100193, China.

ABSTRACT
Pickles are popular in China and exhibits health-promoting effects. However, nitrite produced during fermentation adversely affects health due to formation of methemoglobin and conversion to carcinogenic nitrosamine. Fruiting bodies of the mushroom Boletus edulis were capable of inhibiting nitrite production during pickle fermentation. A 90-kDa nitrite reductase (NiR), demonstrating peptide sequence homology to fungal nitrite reductase, was isolated from B. edulis fruiting bodies. The optimum temperature and pH of the enzyme was 45 °C and 6.8, respectively. B. edulis NiR was capable of prolonging the lifespan of nitrite-intoxicated mice, indicating that it had the action of an antidote. The enzyme could also eliminate nitrite from blood after intragastric administration of sodium nitrite, and after packaging into capsule, this nitrite-eliminating activity could persist for at least 120 minutes thus avoiding immediate gastric degradation. B. edulis NiR represents the first nitrite reductase purified from mushrooms and may facilitate subsequent applications.

No MeSH data available.


The effect of Boletus edulis in decreasing nitrite content during pickles fermention.(a) Differences in changes of nitrite content between pickles in control group (with no addition of mushroom) and experimental group (with addition of mushroom) during the period of fermentation. (b) Percent decrease of nitrite content in pickles of experimental group relative to pickles in control group during the period of fermentation. Results are presented as mean ± SD (n = 3).
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f1: The effect of Boletus edulis in decreasing nitrite content during pickles fermention.(a) Differences in changes of nitrite content between pickles in control group (with no addition of mushroom) and experimental group (with addition of mushroom) during the period of fermentation. (b) Percent decrease of nitrite content in pickles of experimental group relative to pickles in control group during the period of fermentation. Results are presented as mean ± SD (n = 3).

Mentions: To test the effect of fresh B. edulis fruiting bodies on the nitrite content of pickles, the fruiting bodies were added to the pickles (1:1, w-w), and the nitrite level was determined daily throughout the fermentation period, in comparison with pickles without prior exposure to fruiting bodies. A decline in nitrite content in the experimental pickles relative to the untreated control pickles was obvious on the second day of fermentation, and the decrease became even more pronounced on the third to the fifth day. The maximum (97.1%) reduction of nitrite content occurred on the 4th day of fermentation. Thereafter, the difference between the control and experimental groups became attenuated. On the 10th day, there was no discernible difference between the control and experimental groups (Fig. 1). The overall trends of variations in the nitrite content during the fermentation process were consistent, being high initially followed by a decrement. This is in keeping with other reports. In the early stage of fermentation, the intestinal coliform bacteria and Pseudomonas under aerobic conditions will produce nitrite using nitrate in the new materials, accounting for a rise in the nitrite level at the initial stages of fermentation. As the oxygen in the pickles pot decreases and the pH falls due to the metabolic activities of Lactobacillus, the environment is no longer conducive to the survival of nitrate-producing bacteria. Anaerobic bacteria such as nitrite-producing bacteria begin to proliferate massively and there is an accumulation of organic acids and vitamins beneficial to human health. As the nitrite-producing bacteria decrease in number and Lactobacillus causes nitrite to break down, the amount of nitrite gradually declines. Consequently the content of nitrite exhibits a trend of an initial rise and a subsequent fall, forming a conspicuous “nitrite peak”13. Furthermore, we tested the addition of various doses ranging from 10% to 50% B. edulis fresh fruiting bodies to pickles, and found that introduction of 30% fruit bodies was able to decrease the nitrite concentration by 92%.


Boletus edulis Nitrite Reductase Reduces Nitrite Content of Pickles and Mitigates Intoxication in Nitrite-intoxicated Mice.

Zhang W, Tian G, Feng S, Wong JH, Zhao Y, Chen X, Wang H, Ng TB - Sci Rep (2015)

The effect of Boletus edulis in decreasing nitrite content during pickles fermention.(a) Differences in changes of nitrite content between pickles in control group (with no addition of mushroom) and experimental group (with addition of mushroom) during the period of fermentation. (b) Percent decrease of nitrite content in pickles of experimental group relative to pickles in control group during the period of fermentation. Results are presented as mean ± SD (n = 3).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4597360&req=5

f1: The effect of Boletus edulis in decreasing nitrite content during pickles fermention.(a) Differences in changes of nitrite content between pickles in control group (with no addition of mushroom) and experimental group (with addition of mushroom) during the period of fermentation. (b) Percent decrease of nitrite content in pickles of experimental group relative to pickles in control group during the period of fermentation. Results are presented as mean ± SD (n = 3).
Mentions: To test the effect of fresh B. edulis fruiting bodies on the nitrite content of pickles, the fruiting bodies were added to the pickles (1:1, w-w), and the nitrite level was determined daily throughout the fermentation period, in comparison with pickles without prior exposure to fruiting bodies. A decline in nitrite content in the experimental pickles relative to the untreated control pickles was obvious on the second day of fermentation, and the decrease became even more pronounced on the third to the fifth day. The maximum (97.1%) reduction of nitrite content occurred on the 4th day of fermentation. Thereafter, the difference between the control and experimental groups became attenuated. On the 10th day, there was no discernible difference between the control and experimental groups (Fig. 1). The overall trends of variations in the nitrite content during the fermentation process were consistent, being high initially followed by a decrement. This is in keeping with other reports. In the early stage of fermentation, the intestinal coliform bacteria and Pseudomonas under aerobic conditions will produce nitrite using nitrate in the new materials, accounting for a rise in the nitrite level at the initial stages of fermentation. As the oxygen in the pickles pot decreases and the pH falls due to the metabolic activities of Lactobacillus, the environment is no longer conducive to the survival of nitrate-producing bacteria. Anaerobic bacteria such as nitrite-producing bacteria begin to proliferate massively and there is an accumulation of organic acids and vitamins beneficial to human health. As the nitrite-producing bacteria decrease in number and Lactobacillus causes nitrite to break down, the amount of nitrite gradually declines. Consequently the content of nitrite exhibits a trend of an initial rise and a subsequent fall, forming a conspicuous “nitrite peak”13. Furthermore, we tested the addition of various doses ranging from 10% to 50% B. edulis fresh fruiting bodies to pickles, and found that introduction of 30% fruit bodies was able to decrease the nitrite concentration by 92%.

Bottom Line: Pickles are popular in China and exhibits health-promoting effects.The optimum temperature and pH of the enzyme was 45 °C and 6.8, respectively.B. edulis NiR was capable of prolonging the lifespan of nitrite-intoxicated mice, indicating that it had the action of an antidote.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory for Agrobiotechnology and Department of Microbiology, China Agricultural University, Beijing 100193, China.

ABSTRACT
Pickles are popular in China and exhibits health-promoting effects. However, nitrite produced during fermentation adversely affects health due to formation of methemoglobin and conversion to carcinogenic nitrosamine. Fruiting bodies of the mushroom Boletus edulis were capable of inhibiting nitrite production during pickle fermentation. A 90-kDa nitrite reductase (NiR), demonstrating peptide sequence homology to fungal nitrite reductase, was isolated from B. edulis fruiting bodies. The optimum temperature and pH of the enzyme was 45 °C and 6.8, respectively. B. edulis NiR was capable of prolonging the lifespan of nitrite-intoxicated mice, indicating that it had the action of an antidote. The enzyme could also eliminate nitrite from blood after intragastric administration of sodium nitrite, and after packaging into capsule, this nitrite-eliminating activity could persist for at least 120 minutes thus avoiding immediate gastric degradation. B. edulis NiR represents the first nitrite reductase purified from mushrooms and may facilitate subsequent applications.

No MeSH data available.