Impact of microorganisms on key processes of organic acid metabolism during the occurrence and disappearance of paocai pellicle

In vegetable fermentation, pellicle is a common quality deterioration phenomenon. This study investigates the characteristics of glucose, organic acids, amino acids, and biogenic amines during the pellicle occurrence and disappearance of paocai. The results revealed a slight increase in pH of the fermentation system after pellicle occurred, and glucose was the main carbohydrate that microbial activity primary relied on. The microorganisms responsible for pellicle formation consumed organic acids in brine, but the lactic acid in paocai gradually increased and exceeded 25 mg/g. The appearance of pellicle caused a decrease in total free amino acids from 200.390 mg/100 g to 172.079 when pellicle occurred, whereas its impact on biogenic amines was not apparent. Through Kyoto Encyclopedia of Genes and Genomes pathway enrichment of metagenomics sequencing data, screening, and sorting of the key enzymes involved in organic acid metabolism, it was observed that the composition and species of the key microorganisms capable of metabolizing organic acids were more abundant before the appearance of pellicle. When pellicle occurred, lactic acid may be metabolized by Lactobacillus plantarum; in contrast, Lactobacillus and Pichia were associated with citric acid metabolism, and Lactobacillus, Pichia, Saccharomycodes, and Kazachstania were linked to malic acid metabolism. Moreover, Prevotella, Kazachstania, Lactobacillus, Vibrio, and Siphonobacter were implicated in succinic acid metabolism. Additionally, the production of tartaric acid and oxalic acid in paocai and brine resulted from abiotic effects. This knowledge offers a theoretical basis for precise control of paocai fermentation process. PRACTICAL APPLICATION: Our study revealed the specific situation of the metabolites produced by the microorganisms during the pollution and recovery process of pellicle in paocai fermentation, especially the effect of pellicle on the key process of organic acid metabolism. These research results provided theoretical basis for precise control of paocai fermentation.

The role of lipoylation in mitochondrial adaptation to methionine restriction

Dietary methionine restriction (MR) is associated with a spectrum of health-promoting benefits. Being conducive to prevention of chronic diseases and extension of life span, MR can activate integrated responses at metabolic, transcriptional, and physiological levels. However, how the mitochondria of MR influence metabolic phenotypes remains elusive. Here, we provide a summary of cellular functions of methionine metabolism and an overview of the current understanding of effector mechanisms of MR, with a focus on the aspect of mitochondria-mediated responses. We propose that mitochondria can sense and respond to MR through a modulatory role of lipoylation, a mitochondrial protein modification sensitized by MR.

Development of Meat Substitutes from Filamentous Fungi Cultivated on Residual Water of Tempeh Factories

In recent years, there has been an increased motivation to reduce meat consumption globally due to environmental and health concerns, which has driven the development of meat substitutes. Filamentous fungal biomass, commonly known as mycoprotein, is a potential meat substitute since it is nutritious and has filaments to mimic meat fibrils. The current study aimed to investigate the potential use of a cheap substrate derived from the food industry, i.e., residual water in a tempeh factory, for mycoprotein production. The type of residual water, nutrient supplementation, optimum conditions for biomass production, and characteristics of the mycoprotein were determined. The results showed that the residual water from the first boiling with yeast extract addition gave the highest mycoprotein content. The optimum growth condition was a pH of 4.5 and agitation of 125 rpm, and it resulted in 7.76 g/L biomass. The mycoprotein contains 19.44% (w/w) protein with a high crude fiber content of 8.51% (w/w) and a low fat content of 1.56% (w/w). In addition, the amino acid and fatty acid contents are dominated by glutamic acid and polyunsaturated fatty acids, which are associated with an umami taste and are considered healthier foods. The current work reveals that the residual boiling water from the tempeh factory can be used to produce high-quality mycoprotein.

Tryptophan-enriched diet or 5-hydroxytryptophan supplementation given in a randomized controlled trial impacts social cognition on a neural and behavioral level

Understanding of emotions and intentions are key processes in social cognition at which serotonin is an important neuromodulator. Its precursor is the essential amino acid tryptophan (TRP). Reduced TRP availability leads to weaker impulse control ability and higher aggression, while TRP supplementation promotes confidence. In a double-blind placebo-controlled fMRI study with 77 healthy adults, we investigated the influence of a 4 week TRP enriched diet and an acute 5-hydroxytryptophan (5-HTP) intake on two social-cognitive tasks, a moral evaluation and an emotion recognition task. With 5-HTP, immoral behavior without negative consequences was rated as more reprehensible. Additionally, during story reading, activation in insula and supramarginal gyrus was increased after TRP intake. No significant effects of TRP on emotion recognition were identified for the whole sample. Importantly, emotion recognition ability decreased with age which was for positive emotions compensated by TRP. Since the supramarginal gyrus is associated with empathy, pain and related information integration results could be interpreted as reflecting stricter evaluation of negative behavior due to better integration of information. Improved recognition of positive emotions with TRP in older participants supports the use of a TRP-rich diet to compensate for age related decline in social-cognitive processes.

Recent advances in determining protein and amino acid requirements in humans

During the past 25 years a significant amount of research has been conducted to determine amino acid requirements in humans. This is primarily due to advancements in the application of stable isotopes to examine amino acid requirements. The indicator amino acid oxidation (IAAO) method has emerged as a robust and minimally invasive technique to identify requirements. The IAAO method is based on the concept that when one indispensable dietary amino acid (IDAA) is deficient for protein synthesis, then the excess of all other IDAA, including the indicator amino acid, will be oxidized. With increasing intakes of the limiting amino acid, IAAO will decrease, reflecting increasing incorporation into protein. Once the requirement for the limiting amino acid is met there will be no further change in the indicator oxidation. The IAAO method has been systematically applied to determine most IDAA requirements in adults. The estimates are comparable to the values obtained using the more elaborate 24h-indicator amino acid oxidation and balance (24h-IAAO/IAAB) model. Due to its non-invasive nature the IAAO method has also been used to determine requirements for amino acids in neonates, children and in disease. The IAAO model has recently been applied to determine total protein requirements in humans. The IAAO method is rapid, reliable and has been used to determine amino acid requirements in different species, across the life cycle and in disease. The recent application of IAAO to determine protein requirements in humans is novel and has significant implications for dietary protein intake recommendations globally.

Amino acid requirements in humans: with a special emphasis on the metabolic availability of amino acids

Due to advances made in the development of stable isotope based carbon oxidation methods, the determination of amino acid requirements in humans has been an active area of research for the past 2 decades. The indicator amino acid oxidation (IAAO) method developed in our laboratory for humans has been systematically applied to determine almost all indispensable amino acid requirements in adult humans. Nutritional application of experimentally derived amino acid requirement estimates depends upon the capacity of food proteins to meet the amino acid requirements in humans. Therefore, there is a need to know the proportion of dietary amino acids which are bioavailable, or metabolically available to the body for protein synthesis following digestion and absorption. Although this concept is widely applied in animal nutrition, it has not been applied to human nutrition due to lack of data. We developed a new in vivo method in growing pigs to identify the metabolic availability of amino acids in foods using the IAAO concept. This metabolic availability method has recently been adapted for use in humans. As this newly developed IAAO based method to determine metabolic availability of amino acids in foods is suitable for rapid and routine analysis in humans, it is a major step forward in defining the protein quality of food sources and integrating amino acid requirement data with dietary amino acid availability of foods.

Threonine requirement of healthy adults, derived with a 24-h indicator amino acid balance technique

BACKGROUND

Because we question the validity of the 1985 FAO/ WHO/UNU upper requirement for threonine of 7 mg x kg(-1) x d(-1), we proposed a tentative mean requirement of 15 mg x kg(-1) x d(-1).

OBJECTIVE

Our goal was to assess threonine adequacy at 3 test intakes and the consequences of a 6-d compared with a 13-d dietary adaptation phase.

DESIGN

We used a 24-h indicator amino acid balance technique ([1-(13)C]leucine as indicator) to assess the threonine requirement. Fifteen healthy adults were randomly assigned to receive 7, 15, or 46 mg threonine x kg(-1) x d(-1) and were studied after 6 and 13 d of adaptation to the experimental diets. Diets were based on an L-amino acid mixture in which the threonine content was varied. At 1700 on days 6 and 13, a 24-h intravenous [(13)C]leucine tracer infusion protocol was begun to assess leucine oxidation and daily leucine balances.

RESULTS

There was no detectable effect of duration of dietary adaptation in leucine oxidation or balance, but the 24-h leucine oxidation and balances differed significantly between the 7-mg intake and each of the 2 higher intakes (P < 0.05). The latter were not significantly different. The 24-h leucine oxidation rate decreased across threonine intakes (P < 0.01 for main effect of diet, independent of infusion day). Leucine oxidation was highly correlated (r = 0.80) between the 2 dietary adaptation phases across all test intakes.

CONCLUSION

The 1985 FAO/WHO/UNU threonine recommendation is inadequate, and 15 mg x kg(-1) x d(-1) is sufficient to achieve mean indicator (leucine) amino acid balance.

Daily requirement for and splanchnic uptake of leucine in healthy adult Indians

BACKGROUND

The 1985 FAO/WHO/UNU requirement for leucine is too low according to tracer-derived estimates of leucine oxidation and balance in adults from developed regions.

OBJECTIVE

The leucine requirement in populations in developing countries was assessed with use of the 24-h tracer balance method and on the basis of nitrogen balances.

DESIGN

Twenty healthy Indian men were studied during their consumption for 6 d of 2 L-amino acid diets that supplied either 14 and 30 (n = 10) or 22 and 40 (n = 10) mg leucine x kg(-1) x d(-1) in random order. At 1800 on day 7, a 24-h constant intravenous [13C]leucine tracer-infusion protocol was conducted to determine leucine oxidation and daily leucine balance. During the intake of 40 mg leucine/d, [2H3]leucine was given orally to assess the splanchnic uptake of leucine.

RESULTS

Mean 24-h leucine oxidation rates were 29.8, 30.6, 33.6, and 39.3 mg x kg(-1) x d(-1) at leucine intakes of 14, 22, 30, and 40 mg x kg(-1) x d(-1), respectively; daily leucine balances were -16.5, -9.0, -3.3, and 0.5 mg x kg(-1) x d(-1), respectively. Mixed-models linear regression of balance against leucine intake resulted in a zero balance at a leucine intake of 37.3 mg x kg(-1) x d(-1). Nitrogen balances were -12.7, -17.9, -3.9, and 1.0 mg x kg(-1) x d(-1) at leucine intakes of 14, 22, 30, and 40 mg x kg(-1) x d(-1). Regression of nitrogen balance against intake resulted in a zero balance at a leucine intake of 37.6 mg x kg(-1) x d(-1). The first-pass splanchnic uptake of leucine was 45.7% and 33.9% in the fasted and fed periods, respectively.

CONCLUSION

A tentative mean leucine requirement of 40 mg x kg(-1) x d(-1) is proposed for healthy Indian adults, as it is for Western subjects.

Lysine requirements of healthy adult Indian subjects, measured by an indicator amino acid balance technique

BACKGROUND

In an earlier study, using a modification of the indicator amino acid oxidation approach, we concluded that the 1985 FAO/WHO/UNU-proposed lysine requirement of 12 mg x kg(-1) x d(-1) is likely inadequate to maintain body amino acid homeostasis in apparently healthy south Asian subjects and that our proposed requirement of 30 mg x kg(-1) x d(-1) is more appropriate.

OBJECTIVE

We assessed the lysine requirement in a similar population by using 4 test lysine intakes (12, 20, 28, and 36 mg x kg(-1) x d(-1)) with an indicator amino acid balance approach.

DESIGN

Sixteen healthy male Indians were studied during each of 2 randomly assigned 8-d L-amino acid diets that supplied either 12 and 28 or 20 and 36 mg lysine. At 1800 on day 8, a 24-h intravenous [(13)C]leucine tracer-infusion protocol was conducted to assess leucine oxidation and daily leucine balance at each lysine intake.

RESULTS

Mean 24-h leucine oxidation rates decreased significantly (P = 0.005) across different lysine intakes and were 104.1, 97.8, 87.3, and 87.3 mg x kg(-1) x d(-1) at intakes of 12, 20, 28, and 36 mg x kg(-1) x d(-1), respectively; mean 24-h leucine balances were 3.3, 9.1, 19.7, and 20.7 mg x kg(-1) x d(-1), respectively (P = 0.015, mixed-model analysis of variance). Oxidation and balances differed significantly between the lower and higher lysine intakes but were not significantly different between the 12- and 20-mg and 28- and 36-mg test intakes. Two-phase regression analysis indicated a mean breakpoint at 29 mg lysine x kg(-1) x d(-1) in the relation between lysine intake and leucine oxidation or balance.

CONCLUSION

We propose a mean lysine requirement of 30 mg x kg(-1) x d(-1) for healthy Indian adults, which is the same amount we proposed previously for Western populations.

Human adult amino acid requirements: [1-13C]leucine balance evaluation of the efficiency of utilization and apparent requirements for wheat protein and lysine compared with those for milk protein in healthy adults

BACKGROUND

There is considerable debate about the human lysine requirement and the consequent nutritional value of wheat protein.

OBJECTIVE

We used a novel [1-(13)C]leucine balance protocol to examine whether adaptive mechanisms to conserve lysine allow wheat to be utilized more efficiently than expected according to current estimates of lysine requirements and wheat utilization.

DESIGN

Wheat and milk proteins were compared in 6 adults infused for 9 h with L-[1-(13)C]leucine in the postabsorptive state (0-3 h), who were fed half-hourly with low-protein (2% of energy, 3-6 h) and isoenergetic higher-protein (12-13% of energy, 6-9 h) meals providing maintenance energy intakes. From acute measurements of [1-(13)C]leucine balance, we predicted nitrogen balance, the metabolic demand for protein, the efficiency of postprandial protein utilization (PPU), and the requirements for wheat protein and lysine.

RESULTS

Leucine balance was higher after the milk than after the wheat feeding because of the greater inhibition of proteolysis by milk. PPU, calculated as the ratio of Deltanitrogen balance to Deltanitrogen intake between the low-protein and higher-protein periods, was 0.68 +/- 0.06 for wheat and 1.00 +/- 0.09 for milk (P </= 0.001). The estimated average wheat protein requirement (0. 6/PPU) was 0.89 +/- 0.08 g*kg(-)(1)*d(-)(1), indicating a lysine requirement of 23.2 +/- 2.0 mg*kg(-)(1)*d(-)(1). The measured PPU for wheat, 0.68 +/- 0.06, was higher than the value calculated from wheat lysine intake and milk protein lysine deposition, 0.26 +/- 0. 02, and higher than predicted by most published estimates of lysine requirements, apart from a value of 19 mg/kg indicated by nitrogen balance studies.

CONCLUSIONS

The results show that adaptive mechanisms of lysine conservation allow wheat protein to be utilized more efficiently than expected.

Nitrogen and amino acid requirements: : the Massachusetts Institute of Technology amino acid requirement pattern

We review the current international recommendations concerning the protein (nitrogen) and amino acid requirements of healthy individuals, from infancy to the later years of adult life and describe the changes in the recommendations for protein that have been made, since those issued in 1985 by Food and Agriculture Organization/World Health Organization/United Nations University (FAO/WHO/UNU), by the International Dietary Energy Consultative Group. The current international requirements for the specific indispensable amino acids are critiqued briefly, and the rationale and basis for the proposed Massachusetts Institute of Technology (MIT) amino acid requirement pattern are presented. The evidence is then summarized that supports its use in practical considerations of protein nutrition. It is suggested that this MIT amino acid requirement pattern provides the best current estimates of the minimum physiological requirements for the indispensable amino acids in children and adults. It is further concluded that it would be difficult to argue for the continued use of the amino acid requirement values proposed by FAO/WHO/UNU in 1985 in the planning and assessment of dietary protein intakes for population groups worldwide. The MIT amino acid requirement pattern supports and strengthens the relevance of dietary protein quality as an important factor in human protein and amino acid nutrition.

Twenty-four-hour oral tracer studies with L-[1-13C]lysine at a low (15 mg.kg (-1).d (-1) and intermediate (29 mg.kg (-1).d(-1)) lysine intake in healthy adults

BACKGROUND

We proposed previously that the mean lysine requirement value is approximately 30 mg * kg(-)(1) * d(-)(1) rather than the proposed 1985 FAO/WHO/UNU estimate of the upper range of the requirement, which is 12 mg * kg(-)(1) * d(-)(1).

OBJECTIVE

Our objective was to explore the 24-h pattern and rate of whole-body lysine [l-(13)C]oxidation and status of whole-body lysine balance in healthy, young adults given an L-amino acid diet supplying either a low lysine intake (14-15 mg * kg(-)(1) * d(-)(1)) or an intermediate lysine intake (29 mg * kg(-)(1) * d(-)(1)) for 6 d before a continuous tracer study with L-[1-(13)C]lysine.

DESIGN

Five subjects received the low lysine intake, 6 subjects received the intermediate intake, and all were studied by using a standard 24-h oral tracer protocol that was described earlier for studies at a generous lysine intake.

RESULTS

The rate of lysine oxidation was not significantly different between the 12-h fasted and 12-h fed states. The daily oxidation rate (f1.gif" BORDER="0"> +/- SD) was 27. 9 +/- 8.8 and 27.3 +/- 17.6 mg lysine * kg(-)(1) * d(-)(1) for the low- and intermediate-intake groups, respectively (NS). Daily lysine balance was -12.4 +/- 92 and 1.8 +/- 17.7 mg * kg(-)(1) * d(-)(1), respectively (P < 0.025), for the low and intermediate intakes. The balance was significantly less than zero (P < 0.001) for the low intake.

CONCLUSION

The FAO/WHO/UNU lysine requirement value is not sufficient to maintain lysine homeostasis in healthy adults. From the results of this and tracer studies done by others, the mean lysine requirement of healthy adults was determined to be 30 mg * kg(-)(1) * d(-)(1).

The effect of dietary protein on the mineral status of vervet monkeys with special reference to the impact of milk solids on calcium excretion

This study assessed the impact of Westernised and traditional African diets on mineral metabolism in general and calcium status in particular in vervet monkeys. Twelve adult male vervet monkeys (Cercopithecus aethiops), with an average weight of 5+/-0.58 kg each, were divided into two groups of six individuals each and fed traditional diets containing largely maize + legumes (17.4%) or Westernised diets containing milk solids (17.2%) as the source of high crude protein for 8 weeks. Blood was taken at 2-week intervals, the animals were weighed, while urine and stool samples were collected over 24 hours. The monkeys on the milk solids diet had diarrhoea for 6 weeks post-dietary intervention, and produced significantly greater quantities (P<0.02) of stool. These animals also produced significantly more urine (P<0.02). There was no difference in the degree of calciuresis of the two groups, but the monkeys on maize + legume proteins absorbed significantly more calcium during weeks two and six (P<0.04). Furthermore, both groups of monkeys showed a significant decline in plasma calcium levels over the experimental period (P<0.001). The diets had no effect on phosphate levels in the plasma or urine. However, both groups of animals absorbed less phosphate (P<0.09). There was an increasing loss of urinary magnesium (P = 0.03) in both groups, with the milk solids group showing lower plasma levels of this element (P = 0.09). However, the milk solids group lost less magnesium through the stool (P<0.03). In addition, the animals on milk solids showed significant natriuresis (P<0.05), while plasma sodium levels in both groups declined over time (P<0.03). Both diets induced a state of urinary potassium loss (P = 0.0003) and decrease in plasma potassium (P<0.0002). Urinary pH and plasma urea were unaffected by the diets, but the monkeys on maize + legumes excreted significantly less (P<0.001) urinary urea. This study indicates that the milk solids diet compromised mineral homeostasis by interfering with gut and renal functioning, while the traditional African diet did not induce these effects.

Statistical analysis of nitrogen balance data with reference to the lysine requirement in adults

Statistical analysis of nitrogen balance data is an important approach to the estimation of human nutrient requirement. The usual procedure is to regress nitrogen (N) balance on intake and to define the requirement as intake that would produce zero balance. In the actual application of this methodology, there are a number of options, and in the present study we explore the sensitivity of the regression approach to those options. To put this problem into a realistic context, we examine the current controversy over the lysine requirements of healthy adults. From early N balance studies, investigators concluded that the mean requirement was generally less than 10 mg. kg(-1). d(-1), whereas based on recent (13)C-tracer and metabolic studies, we propose a tentative mean requirement of approximately 30 mg. kg(-1). d(-1). Jones et al. (1956) conducted careful N balance studies from which they derived an estimate of lysine requirement of less than about 8 mg. kg(-1). d(-1). We reanalyzed these data with different choices of modes of analysis, mathematical models, and different assumptions concerning the magnitude of miscellaneous N losses. We find that for these data the choice of a specific mathematical model has only a small effect on resultant estimates of requirement, while estimated requirements are very sensitive to amount of unmeasured losses that are assumed and how the model is applied (whether the aggregate data are fitted in one pass to a single model, or the data for each individual subject are fitted to that individual's unique model). Moreover, our reanalysis suggests that the population requirement for lysine is in the range of 17 to 36 mg. kg(-1). d(-1) and strongly supports a lysine requirement value of about 30 mg. kg(-1). d(-1). In general, our results indicate that whenever possible, N balance data should be analyzed using a square root model fitted to individual data and that the median of the individual requirements so derived be used as the estimate of population requirement. Moreover, clearly any statistical analyses of N balance data should include a sensitivity analysis to determine the influence of underlying assumptions. Finally, the finding that these estimates are highly dependent on the assumed amount of N miscellaneous losses recommends that further studies on these losses and of the factors that influence them are essential.

The nutritional value of plant-based diets in relation to human amino acid and protein requirements

The adequacy of plant-based diets in developed and developing countries as sources of protein and amino acids for human subjects of all ages is examined. Protein quantity is shown not to be an issue. Digestibility is identified as a problem for some cereals (millet (Panicum miliaceum) and sorghum (Sorghum sp.)) and generally is poorly understood. Direct measurements of biological value in children are reviewed and scoring is considered. Various existing requirement values for amino acids and especially lysine are reviewed, and it is concluded that stable-isotope studies do not yet provide adequate alternative values of N balance data, which for lysine are robust after recalculation and adjustment. A new maintenance requirement pattern is developed, with higher values than those of Food and Agriculture Organization/World Health Organization/United Nations University (1985) but lower values than the Massachusetts Institute of Technology pattern (Young et al. 1989). Calculations of age-related amino acid requirements are based on most recent estimates of human growth and maintenance protein requirements, a tissue amino acid pattern and the new maintenance amino acid pattern. These values appear valid when used to score plant proteins, since they indicate values similar to or less than the biological value measured directly in young children. When used to score plant-based diets in India, no marked deficiencies are identified. All regions score > 1 for adults, whilst for children scores range from > 1, (Tamil Nadhu) from 6 months of age to 0.78 (West Bengal), rising to 0.9 in the 2-5 year old, consistent with reports that high-lysine maize supports similar weight and height growth to that of casein. Inadequate amino acid supply is not an issue with most cereal-based diets.

Adult human amino acid requirements

This brief review is concerned with the status of our current understanding of the quantitative needs for dietary amino acids in healthy adults. The nutritional significance of the conditionally indispensable amino acids is assessed and the requirements for the indispensable amino acids are discussed. Recent research involving the use of the tracer balance approach is reviewed, and the importance of resolving the current uncertainties regarding adult human amino acid needs is highlighted.