Lactis IO-1 Research Articles

Co-expression of Xylose Transporter and Fructose-Bisphosphate Aldolase Enhances the Utilization of Xylose by Lactococcus lactis IO-1.

The raw material cost of lactic acid fermentation accounts for the main part of the production cost, and this necessitates the exploration of the efficient use of cheap raw materials in lactic acid production. We compared the outcomes of the homologous expressions of xylose transporters (xylFGH, xylE, araE, and xylT), 6-phosphofructokinase (pfkA), fructose-bisphosphate aldolase (fbaA), and their co-expression in Lactococcus lactis IO-1 on lactic acid production using xylose as the raw material. We found that the production rate of lactic acid on xylose fermentation by L. lactis IO-1 overexpressing fbaA was the highest (14.42%). Among the xylose transporters investigated, XylT had the strongest xylose transport capacity in L. lactis IO-1, with an increase in the lactic acid production rate by 10.38%. The genes near the overexpression of fbaA or xylT in the metabolic pathway were more upregulated than the distant genes. The co-expression of fbaA and xylT increased the production rate of lactic acid by 27.84% on xylose fermentation by L. lactis IO-1. This work presents a novel strategy for the simultaneous enhancement of the expression of important genes at the beginning and midway of the xylose metabolic pathway of L. lactis IO-1, which could greatly improve the target production.

Optimisation of pre-harvest sago frond sap for the production of l-lactic acid using Lactococcus lactis IO-1

The major restriction of sago palm plantation is the long maturation period for the starch extraction. As such, alternative commodity has to be identified to increase commercial value of sago palm especially from the by-product. Sago frond has been harvested to have numerous advantages as an alternative substrate for the production of biomaterial and biofuel such as lactic acid and bioethanol. This study focuses on effective approach to maximise the concentration of sugar in the substrate and to identify the ideal concentration of sago frond sap (SFSp) as sole media to produce l-lactic acid and grow L. lactis IO-1. Result shows that SFSp extracted from sago rachis using a roller press machine contained glucose (43.8 g/L), xylose (17.3 g/L) as free sugars and starch (5.55 g/L). Combination of enzymatic hydrolysis and sterilisation pre-treatment was found to maximise the concentration of total carbon source (68 g/L) and sterilised sago frond sap suitable to be used for fermentation process. The ideal concentration of SFSp that was determined at 50% dilution produces the highest amount of l-lactic acid (24.02 g/L) synergist by most efficient sugar consumption (89.93%). The use of SFSp as fermentation medium for l-lactic acid production generated maximum biomass concentration of 14.53 g/L. The utilisation of SFSp extracted from pre-harvest sago frond as substrate promote efficiency of l-lactic acid production associated to exceptional growth performance of L. lactis IO-1. In conclusion, the concept of utilizing by-product from sago palm as novel raw material promise reliable resources and superiority of L. lactis IO-1 to metabolise sugar in SFSp promote lucrative and ethical production of l-lactic acid.

GENOTYPIC AND PHENOTYPIC CHARACTERIZATION OF BACTERIOCINOGENIC LACTIC ACID BACTERIAL STRAINS FOR POSSIBLE BENEFICIAL, VIRULENCE, AND ANTIBIOTIC RESISTANCE TRAITS

Lactic acid bacteria (LAB) are a diverse group of microorganisms that can be found in natural habitats and are used in a wide range of industries, especially in the food sector. They are regarded "Generally Recognized as Safe" and are commonly used as a starter culture, probiotics, and biopreservative. However, some LAB genera are excluded from the "Qualified Presumption of Safety" (QPS) list due to the possibility that they have virulence and antibiotic resistance genetic determinants. The objective of this study was to investigate the beneficial, virulence, and antibiotic resistance-related genes in 10 well-characterized bacteriocinogenic LAB strains. The auto-aggregation, co-aggregation, cell surface hydrophobicity, and bile salt tolerance were also evaluated to examine their potential as bacteriocinogenic probiotics and/or starter culture. Results showed that all tested strains showed abilities for auto-aggregation at 4oC and 37oC, co-aggregation with S. aureus JCM8704, S. typhimurium BIOTECH1826, and E. coli DH5α, and significant cell-surface hydrophobicity. However, only a few strains were able to withstand the media treated with 0.3% bile salt. Among the tested bacteriocinogenic LAB strains, L. lactis IO-1 and C. divergens V41 had the maximum values for auto-aggregation at 4oC and 37oC, respectively. C. divergens V41 also exhibited the highest percentage for cell surface hydrophobicity. E. faecium NKR-5-3 showed the highest co-aggregation percentages with all indicator strains. Our findings also showed that the tested isolates presented distinct combinations of virulence-related genes. Only two of ten bacteriocinogenic LAB strains exhibited presence of multiple virulence genes. Lactococcus sp. QU12 was found to have a high frequency of beneficial and virulence genes, with 2 out of 7 genes present encoding beneficial factor and 11 out of 13 genes encoding virulence factor. Lactococcus sp. QU12 and L. lactis IO-1 were also positive for tetracycline resistance gene tetM and aminoglycoside resistance gene aphA-2, respectively, and transposon genes. Moreover, only a few LAB isolates tested positive for 2 out of 8 antibiotic resistance classes. Although few, the substantial danger of these genes being transferred and acquired cannot be overlooked as this could potentially cause serious health concerns in the future. These results suggest that despite the promising properties of bacteriocinogenic LAB, careful safety evaluation of these strains should be a prerequisite before using these in food systems.

GENOTYPIC AND PHENOTYPIC CHARACTERIZATION OF BACTERIOCINOGENIC LACTIC ACID BACTERIAL STRAINS FOR POSSIBLE BENEFICIAL, VIRULENCE, AND ANTIBIOTIC RESISTANCE TRAITS

Lactic acid bacteria (LAB) are a diverse group of microorganisms that can be found in natural habitats and are used in a wide range of industries, especially in the food sector. They are regarded Generally Recognized as Safe and are commonly used as a starter culture, probiotics, and biopreservative. However, some LAB genera are excluded from the Qualified Presumption of Safety (QPS) list due to the possibility that they have virulence and antibiotic resistance genetic determinants. The objective of this study was to investigate the beneficial, virulence, and antibiotic resistance-related genes in 10 well-characterized bacteriocinogenic LAB strains. The auto-aggregation, co-aggregation, cell surface hydrophobicity, and bile salt tolerance were also evaluated to examine their potential as bacteriocinogenic probiotics and/or starter culture. Results showed that all tested strains showed abilities for auto-aggregation at 4oC and 37oC, co-aggregation with S. aureus JCM8704, S. typhimurium BIOTECH1826, and E. coli DH5α, and significant cell-surface hydrophobicity. However, only a few strains were able to withstand the media treated with 0.3% bile salt. Among the tested bacteriocinogenic LAB strains, L. lactis IO-1 and C. divergens V41 had the maximum values for auto-aggregation at 4oC and 37oC, respectively. C. divergens V41 also exhibited the highest percentage for cell surface hydrophobicity. E. faecium NKR-5-3 showed the highest co-aggregation percentages with all indicator strains. Our findings also showed that the tested isolates presented distinct combinations of virulence-related genes. Only two of ten bacteriocinogenic LAB strains exhibited presence of multiple virulence genes. Lactococcus sp. QU12 was found to have a high frequency of beneficial and virulence genes, with 2 out of 7 genes present encoding beneficial factor and 11 out of 13 genes encoding virulence factor. Lactococcus sp. QU12 and L. lactis IO-1 were also positive for tetracycline resistance gene tetM and aminoglycoside resistance gene aphA-2, respectively, and transposon genes. Moreover, only a few LAB isolates tested positive for 2 out of 8 antibiotic resistance classes. Although few, the substantial danger of these genes being transferred and acquired cannot be overlooked as this could potentially cause serious health concerns in the future. These results suggest that despite the promising properties of bacteriocinogenic LAB, careful safety evaluation of these strains should be a prerequisite before using these in food systems.

Use of the Lactococcus lactis IO-1 for developing a novel functional beverage from coconut water

The goal of this work was to add value to the coconut water (CW) by fermentation with the potential probiotic Lactococcus lactis subsp lactis IO-1 in order to produce fermented CW beverages. Unpasteurized coconut water (UPW) was fermented with Lactococcus lactis subsp lactis IO-1 for 48 h at 30°C, and the viable cell counts, total acidity, pH, degree of polymerization, antioxidant activity, antibacterial bioassay and lethality bioassay were studied at 24 and 48 h. We revealed that the fermentation process of UPW with probiotic L. lactis IO-1 increased the viable cell counts. The total phenolic compound exhibited a higher antioxidative ability in fermented UPW at 48 h (65.79g/mL gallic acid equivalence). The fermented UPW exhibited the highest ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging abilities at 48 h (67.62 and 63.03%), The culture extracted from fermented UPW inhibited all the tested pathogenic foodborne such as Listeria monocytogenes, Salmonella typhi, Staphylococcus aureus, and Escherichia coli, although the degree of antagonistic varied between the pathogens. Furthermore, fermented UPW extract sample at 48 h, exhibited lower potent activity against the brine shrimp with LC50 values (7158.2 µg/mL). Comparatively, pasteurized coconut water (PCW90) fermented by Lactococcus lactis subsp lactis IO-1 produced a fermented beverage PCW90 with similar properties as the fermented UPW. Adding 0.4% (w/v) of coconut flavor and 20% pure honey (v/v) into the fermented CW gave the beverage a better taste. The obtained results showed that the CW product fermented by Lactococcus lactis subsp lactis IO-1 may be used as a novel functional beverage comprising both probiotics and electrolytes, which can serve as a good vehicle for developing a wider range of novel products. Keywords: Antibacterial activity, antioxidant activity, brine shrimp lethality test, coconut water, cytotoxicity.

Genome-scale exploration of transcriptional regulation in the nisin Z producer Lactococcus lactis subsp. lactis IO-1

Transcription is of the most crucial steps of gene expression in bacteria, whose regulation guarantees the bacteria’s ability to adapt to varying environmental conditions. Discovering the molecular basis and genomic principles of the transcriptional regulation is thus one of the most important tasks in cellular and molecular biology. Here, a comprehensive phylogenetic footprinting framework was implemented to predict maximal regulons of Lactococcus lactis subsp. lactis IO-1, a lactic acid bacterium known for its high potentials in nisin Z production as well as efficient xylose consumption which have made it a promising biotechnological strain. A total set of 321 regulons covering more than 90% of all the bacterium’s operons have been elucidated and validated according to available data. Multiple novel biologically-relevant members were introduced amongst which arsC, mtlA and mtl operon for BusR, MtlR and XylR regulons can be named, respectively. Moreover, the effect of riboflavin on nisin biosynthesis was assessed in vitro and a negative correlation was observed. It is believed that understandings from such networks not only can be useful for studying transcriptional regulatory potentials of the target organism but also can be implemented in biotechnology to rationally design favorable production conditions.

Hydroxypropyl methylcellulose enhances the stability of o/w Pickering emulsions stabilized with chitosan and the whole cells of Lactococcus lactis IO-1

Hydroxypropyl methylcellulose (HPMC) was used as a co-emulsifier with chitosan and the whole cells of bacteriocin-producing Lactococcus lactis IO-1 (L. lactis IO-1) for the preparation of bacteria interface Pickering emulsion. The obtained emulsion exhibited a high stability against centrifugation force, ionic strength and low temperature, with the whole cells of L. lactis IO-1 located at the oil/water interface. Because L.lactis IO-1 was found to produce peptide lantibiotic against several strains of Gram-positive food pathogen, the highly stable emulsion demonstrated in this study exhibited high potential as an antimicrobial emulsion with several health benefits of chitosan and HPLC useful for food industry.

Turning hydrophilic bacteria into biorenewable hydrophobic material with potential antimicrobial activity via interaction with chitosan

Alteration of a bacteriocin-producing hydrophilic bacterium, Lactococcus lactis IO-1, into a hydrophobic material with potential antimicrobial activity using chitosan was investigated and compared with five other bacterial species with industrial importance. The negatively charged bacterial cells were neutralized by positively charged chitosan, resulting in a significant increase in the hydrophobicity of the bacterial cell surface. The largest Gram-positive B. megaterium ATCC 14581 showed a moderate response to chitosan while the smaller E. coli DH5α, L. lactis IO-1 and P. putida F1 exhibited a significant response to an increase in chitosan concentration. Because L. lactis IO-1 is a good source for natural peptide lantibiotic that is highly effective against several strains of food spoilage organisms and pathogens, hydrophobic material derived from L. lactis IO-1 and chitosan is a promising novel material with antimicrobial activity for the food and pharmaceutical industries.

Genomic Features ofLactococcus lactisIO-1, a Lactic Acid Bacterium That Utilizes Xylose and Produces High Levels ofL-Lactic Acid

Lactococcus lactis IO-1 (JCM7638) produces L-lactic acid predominantly when grown at high xylose concentrations, and its utilization is highly desired in the green plastics industry. Therefore it is worthwhile studying its genomic traits. In this study, we focused on (i) genes of possible horizontal transfer derivation (prophages, the nisin-sucrose transposon, and several restriction-modification systems), and (ii) genes for the synthetic pathways of amino acids and vitamins in the IO-1 genome. In view of the results of this analysis, we consider their meanings in strain IO-1.

Chemically defined media and auxotrophy of the prolific l-lactic acid producer Lactococcus lactis IO-1

Two chemically defined media, CDM-1G and CDM-1X, that use glucose and xylose as carbon sources, respectively, were prepared for Lactococcus lactis strain IO-1. The maximal cell density at 600nm in CDM-1G exceeded 2. Omission growth experiments indicated that IO-1 is auxotrophic for 2 vitamins and 6 amino acids.

Improved homo l-lactic acid fermentation from xylose by abolishment of the phosphoketolase pathway and enhancement of the pentose phosphate pathway in genetically modified xylose-assimilating Lactococcus lactis

In order to achieve efficient homo L-lactic acid fermentation from xylose, we first carried out addition of xylose assimilation ability to Lactococcus lactis IL 1403 by introducing a plasmid carrying the xylRAB genes from L. lactis IO-1 (pXylRAB). Then modification of xylose assimilation pathway was carried out. L. lactis has two pathways for xylose assimilation called the phosphoketolase pathway (PK pathway) that produces both lactic acid and acetic acid and the pentose phosphate pathway (PP pathway) that produces only lactic acid as a final product. Thus a mutant strain that disrupted its phosphokeolase gene (ptk) was constructed. The Δptk mutant harboring pXylRAB lacked the PK pathway and produced predominantly lactic acid from xylose via the PP pathway, although its fermentation rate slightly decreased. Further introduction of the transketolase gene (tkt) to disrupted ptk locus led restoration of fermentation rate and this was attributed to enhancement of the PP pathway. As a result, ptk::tkt strain harboring pXylRAB produced 50.1 g/l of L-lactic acid from xylose with a high optical purity of 99.6% and a high yield of 1.58 (moles per mole xylose consumed) that is close to theoretical value of 1.67 from xylose.

Kinetic modeling and sensitivity analysis of xylose metabolism in Lactococcus lactis IO-1

We proposed a kinetic simulation model of xylose metabolism in Lactococcus lactis IO-1 that describes the dynamic behavior of metabolites using the simulator WinBEST-KIT. This model was developed by comparing the experimental time-course data of metabolites in batch cultures grown in media with initial xylose concentrations of 20.3-57.8 g/l with corresponding calculated data. By introducing the terms of substrate activation, substrate inhibition, and product inhibition, the revised model showed a squared correlation coefficient (r2) of 0.929 between the experimental time-course of metabolites and the calculated data. Thus, the revised model is assumed to be one of the best candidates for kinetic simulation describing the dynamic behavior of metabolites. Sensitivity analysis revealed that pyruvate flux distribution is important for higher lactate production. To confirm the validity of our kinetic model, the results of the sensitivity analysis were compared with enzyme activities observed during increasing lactate production by adding natural rubber serum powder to the xylose medium. The experimental results on pyruvate flux distribution were consistent with the prediction by sensitivity analysis.

Production of nisin Z using Lactococcus lactis IO-1 from hydrolyzed sago starch

A membrane bioreactor for production of nisin Z was constructed using Lactococcus lactis IO-1 in continuous culture using hydrolyzed sago starch as carbon source. A strategy used to enhance the productivity of nisin Z was to maintain the cells in a continuous growth at high cell concentration. This resulted in a volumetric productivity of nisin Z, as 50,000 IU l(-1) h(-1) using a cell concentration of 15 g l(-1), 30( degrees )C, pH 5.5 and a dilution rate of 1.24 h(-1). Adding 10 g l(-1) YE and 2 g l(-1) polypeptone, other inducers were unnecessary to maintain production of nisin. The operating conditions of the reactor removed nisin and lactate, thus minimizing their effects which allowed the maintenance of cells in continuous exponential growth phase mode with high metabolic activity.

Optimization of lactic acid production by immobilized Lactococcus lactis IO-1

Production of lactic acid from glucose by immobilized cells of Lactococcus lactis IO-1 was investigated using cells that had been immobilized by either entrapment in beads of alginate or encapsulation in microcapsules of alginate membrane. The fermentation process was optimized in shake flasks using the Taguchi method and then further assessed in a production bioreactor. The bioreactor consisted of a packed bed of immobilized cells and its operation involved recycling of the broth through the bed. Both batch and continuous modes of operation of the reactor were investigated. Microencapsulation proved to be the better method of immobilization. For microencapsulated cells at immobilized cell concentration of 5.3 g l(-1), the optimal production medium had the following initial concentrations of nutrients (g l(-1)): glucose 45, yeast extract 10, beef extract 10, peptone 7.5 and calcium chloride 10 at an initial pH of 6.85. Under these conditions, at 37 degrees C, the volumetric productivity of lactic acid in shake flasks was 1.8 g l(-1) h(-1). Use of a packed bed of encapsulated cells with recycle of the broth through the bed, increased the volumetric productivity to 4.5 g l(-1) h(-1). The packed bed could be used in repeated batch runs to produce lactic acid.

Xylooligosaccharide fermentation with Leuconostoc lactis

Strains of Leuconostoc lactis SHO-47 and Le. lactis SHO-54, producing the clinically useful enzyme NAD-specific 6-phosphoglucanate dehydrogenase, were cultivated with a hydrolyzed birch wood xylan as the unique carbon source to produce D-lactic acid for poly(D-lactic acid). In addition to the strains SHO-47 and SHO-54, Lactococcus lactis IO-1, well known as a good xylose-utilizing lactic acid bacterium, was used as a control to confirm the extent of hemicellulose hydrolysis. The fermentation time for lactic acid of strains SHO-47 and SHO-54 was 12 h, and produced respectively 2.3 and 2.2 g/l lactic acid from 8.5 g/l hydrolyzed xylan, whereas the fermentation time of strain IO-1 was 21 h, and produced 1.3 g/l lactic acid. Xylooligosaccharides from xylobiose to xylohexose were utilized more rapidly than xylose in the cultures of strains SHO-47 and SHO-54. However, xylose concentration increased temporarily and then decreased in the culture of strain IO-1. On the other hand, xylooligosaccharides larger than xyloheptaose were not utilized by these three strains. The xylosidase activities of SHO-47, SHO-54, and IO-1 were induced by xylose or a mixture of xylobiose and xylotriose. The xylosidases of these three strains were localized in their cytoplasm.

Restoration of a defective Lactococcus lactis xylose isomerase.

The genes (xylA) encoding xylose isomerase (XI) from two Lactococcus lactis subsp. lactis strains, 210 (Xyl(-)) and IO-1 (Xyl(+)), were cloned, and the activities of their expressed proteins in recombinant strains of Escherichia coli were investigated. The nucleotide and amino acid sequence homologies between the xylA genes were 98.4 and 98.6%, respectively, and only six amino acid residues differed between the two XIs. The purified IO-1 XI was soluble with K(m) and k(cat) being 2.25 mM and 184/s, respectively, while the 210 XI was insoluble and inactive. Site-directed mutagenesis on 210 xylA showed that a triple mutant possessing R202M/Y218D/V275A mutations regained XI activity and was soluble. The K(m) and k(cat) of this mutant were 4.15 mM and 141/s, respectively. One of the IO-1 XI mutants, S388T, was insoluble and showed negligible activity similar to that of 210 XI. The introduction of a K407E mutation to the IO-1 S388T XI mutant restored its activity and solubility. The dissolution of XI activity in L. lactis subsp. lactis involves a series of mutations that collectively eliminate enzyme activity by reducing the solubility of the enzyme.

Two different pathways for D-xylose metabolism and the effect of xylose concentration on the yield coefficient of L-lactate in mixed-acid fermentation by the lactic acid bacterium Lactococcus lactis IO-1.

In lactic acid bacteria, pentoses are metabolized via the phosphoketolase pathway, which catalyzes the cleavage of D-xylulose-5-phosphate to equimolar amounts of glyceraldehyde 3-phosphate and acetylphosphate. Hence the yield coefficient of lactate from pentose does not exceed 1.0 mol/mol, while that of Lactococcus lactis IO-1(JCM7638) at high D-xylose concentrations often exceeds the theoretical value. This suggests that, in addition to the phosphoketolase pathway, L. lactisIO-1 may possess another metabolic pathway that produces only lactic acid from xylose. In the present study, the metabolism of xylose in L. lactisIO-1 was deduced from the product formation and enzyme activities of L. lactisIO-1 in batch culture and continuous culture. During cultivation with xylose concentrations above ca. 50 g/l, the yield coefficient of L-lactate exceeded 1.0 mol/mol while those of acetate, formate and ethanol were very low. At xylose concentrations less than 5 g/l, acetate, formate and ethanol were produced with yield coefficients of about 1.0 mol/mol, while L-lactate was scarcely produced. In cells grown at high xylose concentrations, a marked decrease in the specific activities of phosphoketolase and pyruvate formate lyase (PFL), and an increase in those of transketolase and transaldolase were observed. These results indicate that in L. lactisIO-1 xylose may be catabolized by two different pathways, the phosphoketolase pathway yielding acetate, formate and ethanol, and the pentose phosphate (PP)/glycolytic pathway which converts xylose to L-lactate only. Furthermore, it was deduced that the change in the xylose concentration in the culture medium shifts xylulose 5-phosphate metabolism between the phosphoketolase pathway and the PP/glycolytic pathway in L. lactisIO-1, and pyruvate metabolism between cleavage to acetyl-CoA and formic acid by PFL and the reduction to L-lactate by lactate dehydrogenase.

Synchronized fresh cell bioreactor system for continuous l-(+)-lactic acid production using Lactococcus lactis IO-1 in hydrolysed sago starch

An efficient bioreactor, termed a ‘synchronized fresh cell bioreactor’, was developed and consisted of a pH-dependent substrate feed system coupled with cross flow filtration and turbidity control. The effect of high dilution rate and high cell density coupled with high cell viability on the production of l-lactic acid in continuous culture by Lactococcus lactis IO-1 in enzyme-hydrolysed sago starch medium was investigated. For all changes in dilution rate, cells responded in a synchronized way to the addition of glucose by increasing the rate of biomass formation. Consequently, a glucose-free feed solution was required to maintain the cell concentration at a particular pre-set value. This set-up facilitated the maintenance of the cells in a permanent log phase. At a cell concentration of 15 g l −1 and a feed glucose concentration of 53 g l −1, volumetric LA productivities of 8.2, 19.3 and 33.1 g l −1h −1 were obtained at dilution rates of 0.21, 0.50 and 1.1 h −1, respectively. The respective residual glucose concentrations in the spent medium were 1.90, 0.24 and 3.80 g l −1. By increasing the cell density, the volumetric productivity increased proportionally. At high cell density, higher dilution rates resulted in lower lactate concentrations in the culture medium resulting in higher productivity. This reactor facilitated efficient operation with high cell viability by maintaining the cells in continuous growth phase for long-term fermentation. Therefore, the growth rate (μ) was calculated according to the Monod equation. Using this system, high specific productivities can be obtained which guarantees high commercial productivity at economical cost with only a small investment for setting up the sago industry.

Biosynthetic production of nisin Z by immobilized Lactococcus lactis IO-1

Nisin Z, a natural nisin variant, is a lantibiotic that contains unusual amino acids. The immobilization technique was applied to improve the productivity of nisin Z, the peptide antibiotic produced by Lactococcus lactis IO-1. Both entrapment and adsorption methods of immobilization were studied with several kinds of materials in repeated fermentation. The long-term application of natural materials was limited because of the instability of the gel. Low growth rate and low productivity were obtained from the entrapment method due to the improper diffusion of nutrients through the materials. Moreover, the method to entrap the cells with photo-crosslinkable resin prepolymers caused damage to the cells. The adsorption method showed better results compared with the entrapment method. The adsorption of the cells on porous chitosan beads, Chitopearl SH-2510, gave nisin Z productivity about 1.7 times greater than the free cells. However, during the repeated cultivation, a decrease in nisin Z activity was observed. The cells adsorbed on photo-crosslinked resin gel beads, ENTG-3800, produced a greater amount of nisin Z and a lower level of lactic acid than the free cells with a good operational stability. The nisin Z production tended to increase with repeated cultivation. Continuous fermentation was introduced to improve the nisin Z productivity. Free cells showed a good productivity at the dilution rate of 0.1 h −1. However, nisin Z production was affected by cell washout at the dilution rate of 0.2 h −1. The cells adsorbed on ENTG-3800 gel beads displayed an improvement in productivity at higher dilution rates.

Purification, identification, and effective production of a peptide antibiotic produced by Lactococcus lactis IO-1 (JCM 7638).

Annals of the New York Academy of SciencesVolume 864, Issue 1 p. 422-427 Purification, Identification, and Effective Production of a Peptide Antibiotic Produced by Lactococcus lactis IO-1 (JCM 7638) HIROMI MATSUSAKI, HIROMI MATSUSAKI Polymer Chemistry Laboratory; The Institute of Physical and Chemical Research (RIKEN); Saitama 351–01, JapanSearch for more papers by this authorNOPPAWAN CHINACHOTI, NOPPAWAN CHINACHOTI Department of Food Science and Technology; Faculty of Agriculture; Kyushu University; Fukuoka 812–81, JapanSearch for more papers by this authorKENJI SONOMOTO, KENJI SONOMOTO Department of Food Science and Technology; Faculty of Agriculture; Kyushu University; Fukuoka 812–81, JapanSearch for more papers by this authorAYAAKI ISHIZAKI, AYAAKI ISHIZAKI Department of Food Science and Technology; Faculty of Agriculture; Kyushu University; Fukuoka 812–81, JapanSearch for more papers by this author HIROMI MATSUSAKI, HIROMI MATSUSAKI Polymer Chemistry Laboratory; The Institute of Physical and Chemical Research (RIKEN); Saitama 351–01, JapanSearch for more papers by this authorNOPPAWAN CHINACHOTI, NOPPAWAN CHINACHOTI Department of Food Science and Technology; Faculty of Agriculture; Kyushu University; Fukuoka 812–81, JapanSearch for more papers by this authorKENJI SONOMOTO, KENJI SONOMOTO Department of Food Science and Technology; Faculty of Agriculture; Kyushu University; Fukuoka 812–81, JapanSearch for more papers by this authorAYAAKI ISHIZAKI, AYAAKI ISHIZAKI Department of Food Science and Technology; Faculty of Agriculture; Kyushu University; Fukuoka 812–81, JapanSearch for more papers by this author First published: 07 February 2006 https://doi.org/10.1111/j.1749-6632.1998.tb10351.xCitations: 8Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume864, Issue1ENZYME ENGINEERING XIVDecember 1998Pages 422-427 RelatedInformation