Isolation of alkaliphilic bacteria for production of high optically pure L-(+)-lactic acid

Abstract

Lactic acid bacteria that grow under alkaline conditions (pH 10) were isolated from various sources in Okinawa (Japan). These alkali-tolerant and alkaliphilic bacteria were classified as follows: Microbacterium sp. Key words: alkaliphilic bacteria; batch fermentation; Enterococcus casseliflavus; glucose; L-lactic acid Introduction L-Lactic acid is an important metabolite for industrial production of bioplastic materials, and the demand for its expansion in the future is highly expected. Though this optical isomer is obtained by fermentation using microorganisms, both D-and L-type isomers are in the metabolites of common lactic acid bacteria. Microorganisms that produce L-lactic acid with high optical purity are desirable for production of high quality bioplastic materials. For instance, high optically active L-lactic acid production by Lactobacillus sp. (Hujanen and Linko, 1996) and Rhizopus sp. (Kitpreechavanich et al., 2008) has been investigated. Various methods for fermentative production of L-lactic acid by these lactic acid microbes have been examined; however, there is still a need to search for reliable strains to establish efficient production.Approaches to obtain microorganisms from various environments are very important in the development of biotechnology. These isolates help us to understand their role in the environment, and the valuable strains among them are able to contribute to industrial applications. It is difficult to isolate all microorganisms existing in the environment because their growth conditions are different; however, we were able to understand the microbial community by using different conditions for isolation. There must be many isolates that were missed by using growth conditions for dominant microbes in their existing environment. For example, different pH conditions significantly change the type of microbes. Isolation under alkaline conditions makes it possible to obtain some alkaliphilic microorganisms from common sea water as well as special alkali environments. Properties of the microorganisms obtained by different screening methods will give new insights.Lactic acid bacteria are well known to grow under various ranges of neutral and acidic pHs. However, over the past few years, alkaliphilic lactic acid bacteria (Alkalibacterium, Halolactibacillus and Marinilactibacillus species) with optimum growth at pH 7.0 11.5 have been reported (Ishi kawa et al., 2003(Ishi kawa et al., , 2005(Ishi kawa et al., , 2009Nakajima et al., 2005;Ntougias and Russell, 2001;Toffin et al., 2005;Yumoto et al., 2004Yumoto et al., , 2008. Cultivation under alkaline conditions could prevent the risk of bacterial contamination. Alkaliphilic bacteria can provide a method for easier management of fermentative production by suppressing other bacteria at high pH. Some studies have shown that alkaliphilic bacteria Full PaperIsolation of alkaliphilic bacteria for production of high optically pure L-(+)-lactic acid (Received March 5, 2014; Accepted September 24, 2014) Hiroto Yokaryo* and Yutaka Tokiwa Ok...

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“…Except for an alkalophilic Bacillus sp. WL-S20 that produced 225g/l from glucose at a yield of 99.3g/g using multi-pulse Fed batch fermentation [7], the final LA concentration (140.8g/l) and LA yield (0.93-0.99g/g of glucose consumed) obtained in the current study under alkaliphilic condition using the green neutralizer (NaOH) to maintain the pH during fermentation were acceptable when compared with other wilD-type alkaliphilic strains e.g Halolactibacillus halophilus (65.8g/l L-LA with yield of 0.76g/g) [10], Exiguobacterium 8-11-1 (125g/l of L-LA with a yield of 0.98g/g) [12], Enterococcus casseliflavus 79w3 (103g/l of L-LA with yield of 0.80g/g) [13].…”

“…Alkaliphilic strains can also considered good producers for organic acids [11]. Very few alkaliphilic strains have been reported for LA production from glucose such as Halolactibacillus halophilus that produced 65.8g/l L-LA in batch fermentation at pH 9.0 with a low yield of 0.76g/g [10], Exiguobacterium 8-11-1 strain produced 125g/l of L-LA with a yield of 0.98g/g in Fed batch fermentation at pH 8.5 [12], Enterococcus casseliflavus 79w3 that produced 103g/l of L-LA with a low yield of 0.80g/g at pH 8.0 in batch fermentation [13] and genetically modified Bacillus N16-5 that produced 143.9g/l of D-LA with a yield of 96.1g/g of glucose consumed in Fed batch fermentation [14]. These studies either reported a low concentration of LA with low yield or performed at slightly alkaline conditions that increase the risk of contamination, in addition to the expected instability of genetically modified organisms.…”

Potential pyruvate and poly (3- hydroxybutyrate) production of halophiles bacteria isolated from Giao Thuy, Nam Dinh’s mangrove forest

“…Mặc dù hàm lượng pyruvate của chủng ND7 cao hơn rất nhiều so với công bố trước đó của Ngô Thị Hoài Thu và nnk., (2018) (0,11 g/L) nhưng vẫn còn thấp để có thể sử dụng để sản xuất pyruvate ở quy mô lớn hơn. Nghiên cứu của Kawata et al (2016) Theo công bố của Calabia et al, (2011), Yokaryo & Tokiwa (2014) các chủng vi khuẩn có khả năng chịu kiềm là những chủng tiềm năng để sản xuất các axit hữu cơ trong đó có pyruvate. Kawata et al (2016) đã phát hiện khả năng pyruvate được tiết ra môi trường nuôi cấy lên tới 63,3 g/L sau 48 giờ nuôi chủng vi khuẩn Halomonas sp.…”

Recent Progress in the Microbial Production of Pyruvic Acid

“…Being naturally tolerant to salt and osmotic pressure, halophilic microbes have recently gained attention for microbial production of organic acids [45][46][47]. One alkaliphilic, halophilic Halomonas generated 63 g/L pyruvate in 48 h under aerobic conditions using an unsterilized defined medium having high ionic strength [48].…”