High-titer and productivity of l-(+)-lactic acid using exponential fed-batch fermentation with Bacillus coagulans arr4, a new thermotolerant bacterial strain

Integrated lactic acid production from lignocellulosic agricultural wastes under thermal conditions

The production of lactic acid (LA) from agricultural wastes attracts great attention because of the sustainability and abundance of lignocellulosic feedstocks, as well as the increasing demand for biodegradable polylactic acid. In this study, we isolated a thermophilic strain Geobacillus stearothermophilus 2H-3 for use in robust production of L-(+)LA under the optimal conditions of 60 °C, pH 6.5, which were consistent with the whole-cell-based consolidated bio-saccharification (CBS) process. Sugar-rich CBS hydrolysates derived from various agricultural wastes, including corn stover, corncob residue, and wheat straw, were used as the carbon sources for 2H-3 fermentation by directly inoculating 2H-3 cells into the CBS system, without intermediate sterilization, nutrient supplementation, or adjustment of fermentation conditions. Thus, we successfully combined two whole-cell-based steps into a one-pot successive fermentation process to efficiently produce LA with high optical purity (99.5%), titer (51.36 g/L), and yield (0.74 g/g_biomass). This study provides a promising strategy for LA production from lignocellulose through CBS and 2H-3 fermentation integration.

Bioproduction of l- and d-lactic acids: advances and trends in microbial strain application and engineering

Lactic acid is an important platform chemical used in the food, agriculture, cosmetic, pharmaceutical, and chemical industries. It serves as a building block for the production of polylactic acid (PLA), a biodegradable polymer, which can replace traditional petroleum-based plastics and help to reduce environmental pollution. Cost-effective production of optically pure l- and d-lactic acids is necessary to achieve a quality and thermostable PLA product. This paper evaluates research advances in the bioproduction of l- and d-lactic acids using microbial fermentation. Special emphasis is given to the development of metabolically engineered microbial strains and processes tailored to alternative and flexible feedstock concepts such as: lignocellulose, glycerol, C1-gases, and agricultural-food industry byproducts. Alternative fermentation concepts that can improve lactic acid production are discussed. The potential use of inducible gene expression systems for the development of biosensors to facilitate the screening and engineering of lactic acid-producing microorganisms is discussed.

Production of L (+) Lactic Acid by Lactobacillus casei Ke11: Fed Batch Fermentation Strategies

Lactic acid and its derivatives are widely used in pharmaceutical, leather, textile and food industries. However, until now there have been few systematic reports on fed-batch fermentation for efficient production and high concentration of l-lactic acid by lactic acid bacteria. This study describes the obtainment of L (+) lactic acid from sucrose using the Lactobacillus casei Ke11 strain through different feeding strategies using an accessible pH neutralizer such as CaCO3. The exponential feeding strategy can increase lactic acid production and productivity (175.84 g/L and 3.74 g/L/h, respectively) with a 95% yield, avoiding inhibition by high initial substrate concentration and, combined with the selected agent controller, avoids the cellular stress that could be caused by the high osmotic pressure of the culture media. The purification of the acid using charcoal and celite, followed by the use of a cation exchange column proved to be highly efficient, allowing a high yield of lactic acid, high removal of sugars and proteins. The described process shows great potential for the production of lactic acid, as well as the simple, efficient and low-cost purification method. This way, this work is useful to the large-scale fermentation of L. casei Ke11 for production of l-lactic acid.

Kinetic characteristics of long-term repeated fed-batch (LtRFb) l-lactic acid fermentation by a Bacillus coagulans strain

Application of degradable plastics is the most critical solution to plastic pollution. As the precursor of biodegradable plastic PLA (polylactic acid), efficient production of l-lactic acid is vital for the commercial replacement of traditional plastics. Bacillus coagulans H-2, a robust strain, was investigated for effective production of l-lactic acid using long-term repeated fed-batch (LtRFb) fermentation. Kinetic characteristics of l-lactic acid fermentation were analyzed by two models, showing that cell-growth coupled production gradually replaces cell-maintenance coupled production during fermentation. With the LtRFb strategy, l-lactic acid was produced at a high final concentration of 192.7 g/L, on average, and a yield of up to 93.0% during 20 batches of repeated fermentation within 487.5 h. Thus, strain H-2 can be used in the industrial production of l-lactic acid with optimization based on kinetic modeling.

Fermentation for tailoring the technological and health related functionality of food products

Fermented foods are experiencing a resurgence due to the consumers' growing interest in foods that are natural and health promoting. Microbial fermentation is a biotechnological process which transforms food raw materials into palatable, nutritious and healthy food products. Fermentation imparts unique aroma, flavor and texture to food, improves digestibility, degrades anti-nutritional factors, toxins and allergens, converts phytochemicals such as polyphenols into more bioactive and bioavailable forms, and enriches the nutritional quality of food. Fermentation also modifies the physical functional properties of food materials, rendering them differentiated ingredients for use in formulated foods. The science of fermentation and the technological and health functionality of fermented foods is reviewed considering the growing interest worldwide in fermented foods and beverages and the huge potential of the technology for reducing food loss and improving nutritional food security.

Steps Toward High-Performance PLA: Economical Production of d-Lactate Enabled by a Newly Isolated Sporolactobacillus terrae Strain

Optically pure d-lactate production has received much attention for its critical role in high-performance polylactic acid production. However, the current technology can hardly meet the comprehensive demand of industrialization on final titer, productivity, optical purity, and raw material costs. Here, an efficient d-lactate producer strain, Sporolactobacillus terrae (S. terrae) HKM-1, is isolated for d-lactate production. The strain HKM-1 shows extremely high d-lactate fermentative capability by using peanut meal, soybean meal, or corn steep liquor powder as a sole nitrogen source; the final titers (205.7 g L-1 , 218.9 g L-1 , and 193.9 g L-1 , respectively) and productivities (5.56 g L-1  h-1 , 5.34 g L-1  h-1 , and 3.73 g L-1  h-1 , respectively) of d-lactate reached the highest level ever reported. A comparative genomic analysis between S. terrae HKM-1 and previously reported d-lactate high-producing Sporolactobacillus inulinus (S. inulinus) CASD is conducted. The results show that many unrelated genetic features may contribute to the superior performance in d-lactate production of S. terrae HKM-1. This d-lactate producer HKM-1, along with its fermentation process, is promising for sustainable d-lactate production by using agro-industrial wastes.

Potential Use of Bacillus coagulans in the Food Industry

Probiotic microorganisms are generally considered to beneficially affect host health when used in adequate amounts. Although generally used in dairy products, they are also widely used in various commercial food products such as fermented meats, cereals, baby foods, fruit juices, and ice creams. Among lactic acid bacteria, Lactobacillus and Bifidobacterium are the most commonly used bacteria in probiotic foods, but they are not resistant to heat treatment. Probiotic food diversity is expected to be greater with the use of probiotics, which are resistant to heat treatment and gastrointestinal system conditions. Bacillus coagulans (B. coagulans) has recently attracted the attention of researchers and food manufacturers, as it exhibits characteristics of both the Bacillus and Lactobacillus genera. B. coagulans is a spore-forming bacterium which is resistant to high temperatures with its probiotic activity. In addition, a large number of studies have been carried out on the low-cost microbial production of industrially valuable products such as lactic acid and various enzymes of B. coagulans which have been used in food production. In this review, the importance of B. coagulans in food industry is discussed. Moreover, some studies on B. coagulans products and the use of B. coagulans as a probiotic in food products are summarized.