Biocatalyst development for lactic acid production at acidic pH using inter-generic protoplast fusion

Singhvi, Mamata; Gurjar, Gayatri; Gupta, Vidya S.; Gokhale, D. V.

doi:10.1039/c4ra11104d

Cited by 18 publications

(6 citation statements)

References 36 publications

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“…For example, for free lactic acid production from LAB, neutralizing agents such as calcium carbonate are required for promoting lactic acid yield, which may reflect that LAB strains are still sensitive to organic week acids even they possess AR mechanisms (Liu et al, 2015; Singhvi et al, 2018). In addition, production of lactic acid at acidic environments without neutralizing agents can be achieved by constructing protoplast fusion using A. pasteurianus and Lactobacillus delbrueckii Uc-3 (Singhvi et al, 2015), suggesting the robust protection against organic acid could be provided by distinguishing AR systems in AAB.…”

Section: Discussionmentioning

confidence: 99%

Bacterial Acid Resistance Toward Organic Weak Acid Revealed by RNA-Seq Transcriptomic Analysis in Acetobacter pasteurianus

Yang

Yu²,

Fu³

et al. 2019

Front. Microbiol.

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Under extreme acidic environments, bacteria exploit several acid resistance (AR) mechanisms for enhancing their survival, which is concerned with several aspects, such as issues in human health and fermentation for acidic products. Currently, knowledge of bacterial AR mainly comes from the strong acid (such as hydrochloric acid) stresses, whereas AR mechanisms against organic weak acids (such as acetic acid), which are indeed encountered by bacteria, are less understood. Acetic acid bacteria (AAB), with the ability to produce acetic acid up to 20 g/100 mL, possess outstanding acetic acid tolerance, which is conferred by their unique AR mechanisms, including pyrroloquinoline quinine-dependent alcohol dehydrogenase, acetic acid assimilation and molecular chaperons. The distinguished AR of AAB toward acetic acid may provide a paradigm for research in bacterial AR against weak organic acids. In order to understand AAB’s AR mechanism more holistically, omics approaches have been employed in the corresponding field. However, the currently reported transcriptomic study was processed under a low-acidity (1 g/100 mL) environment, which could not reflect the general conditions that AAB are usually faced with. This study performed RNA-Seq transcriptomic analysis investigating AR mechanisms in Acetobacter pasteurianus CGMCC 1.41, a widely used vinegar-brewing AAB strain, at different stages of fermentation, namely, under different acetic acid concentrations (from 0.6 to 6.03 g/100 mL). The results demonstrated the even and clustered genomic distribution of up- and down-regulated genes, respectively. Difference in AR between AAB and other microorganisms was supported by the down-regulation of urea degradation and trehalose synthesis-related genes in response to acetic acid. Detailed analysis reflected the role of ethanol respiration as the main energy source and the limited effect of acetic acid assimilation on AR during fermentation as well as the competition between ethanol respiratory chain and NADH, succinate dehydrogenase-based common respiratory chain. Molecular chaperons contribute to AR, too, but their regulatory mechanisms require further investigation. Moreover, pathways of glucose catabolism and fatty acid biosynthesis are also related to AR. Finally, 2-methylcitrate cycle was proposed as an AR mechanism in AAB for the first time. This study provides new insight into AR mechanisms of AAB, and it also indicates the existence of numerous undiscovered AR mechanisms.

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Section: Discussionmentioning

confidence: 99%

Bacterial Acid Resistance Toward Organic Weak Acid Revealed by RNA-Seq Transcriptomic Analysis in Acetobacter pasteurianus

Yang

Yu²,

Fu³

et al. 2019

Front. Microbiol.

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“…• Fed-batch and continuous cultures 7,22,50,51 • Osmotic-resistant bacteria 28,38 • Osmoprotectants 39 LA and pH growth inhibition • Isolated, engineered or adapted bacteria to low pH 19,71,72 • Using an effective neutralizing agent 40 • LA recovery using membrane extractive fermentation 26,32 Inhibitors released during pretreatment • Isolated, adapted or engineered bacteria with increased tolerance to inhibitors 24,42,[56][57][58][59][60][61] • Optimization of pretreatment and hydrolysis methods to minimize inhibitors' formation 46 Review: Lactic acid production by lactic acid bacteria Th e degradation products produced in the lignocellulosic biomass pretreatment can be divided into three groups: furan derivatives, weak acids, and phenolic compounds. Th e main furans are furfural and 5-hydroxymethyl furfural (HMF) derived from degradation of pentoses and hexoses, respectively, which cause a prolonged lag phase during batch fermentation.…”

Section: Challengesmentioning

confidence: 99%

“…19 Similarly, a mutant that produced fi vefold more LA at acidic pH was generated using protoplast fusion between L. delbrueckii Mut Uc-3 and the acid-tolerant Acetobacter pasteurianus. 72 Error-prone amplifi cation of L. pentosus genomic DNA allowed the isolation of a mutantproducing 17-fold LA at pH 3.8. 71…”

Section: Genetic Engineeringmentioning

confidence: 99%

Biotechnological advances in lactic acid production by lactic acid bacteria: lignocellulose as novel substrate

Cubas-Cano

González‐Fernández

Ballesteros

et al. 2018

Biofuels Bioprod Bioref

153

101

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The production of high added-value products from lignocellulose is proposed as a suitable alternative to petroleum-based resources in terms of environmental preservation, sustainability, and circular economy. Lactic acid is a versatile building block that can be produced via fermentative routes by several groups of microorganisms, including yeasts and microalgae, which are bacteria recognized to achieve the highest concentrations. Lactic acid, among other substances, can be used as a starting point in the production of poly-lactic acid, which is a biopolymer with many applications due to its resistance, durability, biodegradability, and biocompatibility. Lactic acid production can be performed from lignocellulosic biomass. However, lactic acid production from lignocellulose faces several hurdles such as carbohydrate hydrolysis to release sugars, the co-utilization of sugar mixtures by the fermenting microorganism, and the presence of degradation compounds released during pretreatment. In this review, a general overview of lactic-acid bacterial fermentation from lignocellulose is provided, starting from the potential substrates and their composition, the different metabolic pathways involved, and the purifi cation steps. The main challenges are discussed and the newest approaches to solve the limitations of the process are proposed.

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“…Acetobacter strains are responsible for the formation of acetic acid from different substrates. This strain is reported in different studies as able to form acetic acid from starting substrates such as carbohydrates, ethanol, and hydrogen plus carbon dioxide [ 48 , 49 ]. Despite the high abundance of Acetobacter in the fermentation broth, the concentration of acetic acid in phase III was relatively low reaching only 0.48 g COD/L and 2.51 g COD/L in R1 and R2, respectively.…”

Section: Discussionmentioning

confidence: 99%

Lactic acid fermentation of food waste at acidic conditions in a semicontinuous system: effect of HRT and OLR changes

Pau

Tan

Arriaga

et al. 2022

Biomass Conv. Bioref.

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Lactic acid production through fermentation is an established technology, however, improvements are necessary to reduce the process costs and to decrease its market price. Lactic acid is used in many industrial sectors and its market has increased in the last decade for its use as the raw material for polylactic acid product. Using food waste as a cheap and renewable substrate, as well as fermentation at uncontrolled pH, helps to make the production cheaper and to simplify the downstream purification process. Lactic acid production at acidic conditions and the role of varying organic loading rate (OLR) and hydraulic retention time (HRT) were tested in two different semicontinuous batch fermentation systems. Reactor performances indicated that lactic acid fermentation was still possible at pH < 3.5 and even up to a pH of 2.95. The highest lactic acid production was recorded at 14-day HRT, 2.14 g VS/L·day OLR, and pH 3.11 with a maximum lactic acid concentration of 8.72 g/L and a relative yield of 0.82 g lactate/g carbohydrates. The fermentation microbial community was dominated by Lactobacillus strains, the organism mainly responsible for lactic acid conversion from carbohydrates. This study shows that low pH fermentation is a key parameter to improve lactic acid production from food waste in a semicontinuous system. Acidic pH favored both the selection of Lactobacillus strains and inhibited VFA producers from utilizing lactic acid as primary substrate, thus promoting the accumulation of lactic acid. Finally, production yields tend to decrease with high OLR and low HRT, while lactic acid production rates showed the opposite trend.

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Biocatalyst development for lactic acid production at acidic pH using inter-generic protoplast fusion

Abstract: Acid tolerance of L. delbrueckii Mut Uc-3 has been improved using an inter-generic protoplast fusion approach. The fusant was further treated with UV mutagenesis which generated a mutant with improved lactic acid production in acidic environment.

Cited by 18 publications

References 36 publications

Bacterial Acid Resistance Toward Organic Weak Acid Revealed by RNA-Seq Transcriptomic Analysis in Acetobacter pasteurianus

Bacterial Acid Resistance Toward Organic Weak Acid Revealed by RNA-Seq Transcriptomic Analysis in Acetobacter pasteurianus

Biotechnological advances in lactic acid production by lactic acid bacteria: lignocellulose as novel substrate

Lactic acid fermentation of food waste at acidic conditions in a semicontinuous system: effect of HRT and OLR changes

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