Bio-based Lactic Acid Research Articles

Monothiolactide, a New Monomer for the Synthesis of Recyclable, Alternating Ester-Thioester Polymers.

Aliphatic polyesters and polythioesters are very interesting alternatives for current fossil-based and degradation-resistant plastics, due to their high (bio)degradability and (chemical) recyclability potential. Two important examples include polylactide (PLD), currently leading the synthetic bioplastics market, and its sulfur analog polythiolactide (PTLD). Both polymers can be made by ring-opening polymerization (ROP) of their corresponding (thio)dilactones, lactide (LD) and thiolactide (TLD) respectively. In this work, the benefits of esters and thioesters were combined in one material by the successful catalytic synthesis and ROP of monothiolactide (MTL), an unprecedented monomer containing half a LD and half a TLD structural unit. MTL can be obtained by a simple direct condensation of biobased lactic acid and thiolactic acid aided by Brønsted acid catalysis. The novel, but simple monomer showed to be easily polymerized with triethylamine to materials containing alternating lactic and thiolactic ester units with a very high molar mass. The lower stability of MTL (vs. TLD) resulted in improved ROP thermodynamics, while also fast and controllable polymerization kinetics were observed. The new polymers feature a good chemical recycling and hydrolytic degradation potential with important improvements compared to PTLD and PLD. Finally, a successful co-polymerization with commercial LD was shown, paving the way towards industrialization.

Merging biomass and CO2 utilization; process design and assessment on simultaneous production of lactic acid and formic acid from glycerol and CO2

Biomass and CO2 conversion is receiving great attention to address climate change and energy crisis. Bio-based lactic acid (LA) appeals industries, however, current technologies suffer from low productivity and waste production. The transfer hydrogenation of glycerol and CO2 to LA and formic acid (FA) has been proposed as an alternative pathway, but further development and process design are required. This study proposes the integrated process for conversion of glycerol and CO2 to LA and FA derivatives. A two-pot/two-step transfer hydrogenation was demonstrated to achieve high products yield, catalyst reusability, and product separation. The esterification of lactate and formate salts to corresponding esters utilizing CO2 was also developed, which reduces H2SO4 consumption and K2SO4 waste. Techno-economic and life cycle assessments reveal that CO2 utilization is crucial for high economic benefit and low climate change impact. This study shows integrating biomass and CO2 could have synergies to design greener process.

Influence of the Synthesis Protocol on the Catalytic Performance of PHI-Type Zeolites for the Dehydration of Lactic Acid

Acrylic acid is an important basic chemical and a key starting compound for a variety of consumer products. Today, acrylic acid is still produced from fossil-based propene. If acrylic acid were produced from bio-based lactic acid, this would be an important step towards sustainability. The gas-phase dehydration reaction of lactic acid to acrylic acid was performed over eight-membered ring PHI-type zeolites in the Na+ and K+-form. A few variations in the synthesis procedure of PHI-type zeolite made a big difference in the performance during the catalytic reaction due to differences in the physical and chemical properties, especially the accessibility of the pores. The catalysts were characterized with ICP-OES, XRD, CO2 physisorption, SEM and 27Al MAS NMR. The calcination resulted in a partial collapse of the PHI structure. In the case of Na,K-PHI with a low surface area, the catalysis tends to take place on the outer surface, while in the case of Na,K-PHI with a high surface area the catalysis can also take place within the pore system. This has a considerable influence on the selectivity of the catalysts.

Oil Palm Biomass Pretreatment and Hydrolysis: A Recent Biotechnological Venture Towards Bio-Based Lactic Acid Production

The effective utilisation of lignocellulosic biomass as fossil-based counterparts in the development of bio-based chemicals manufacturing is progressively relevant. Hence, many works are underway to shift from petrochemical industries to a sustainable lignocellulosic biomass biorefinery in lactic acid production. Malaysia is the leading country as a palm oil producer, with an enormous supply of inexpensive, renewable and non-food, yet untapped oil palm biomass resources. In this regard, oil palm fronds (OPF) rich in glucan content account for 60% of total agricultural biomass in Malaysia, which can accommodate 2 million metric tons per annum of fermentable sugar. The richness of carbohydrates in OPF serves as the key to unlocking bio-based lactic acid commercialization for future sustainable breakthroughs. This paper aims to provide insights into the exploitation of OPF as the novel feedstocks in bio-refinery processes. Special emphasis in this review is put on the technology, global demand, commercial status and future prospects of the production of second-generation lactic acid, as this process has received most research and development efforts so far. It reviews the current research attributed to the compositional analysis of OPF by primarily focusing on the National Renewable Energy Laboratories (NREL) protocol. It then focuses on the recent technological advancements of different pretreatment methods and hydrolysis for carbohydrate recovery in lactic acid production. Given with the tremendous potential, OPF can be exploited as an excellent sugar platform for the production of higher value products such as advanced biofuels, fine-platform chemicals and bioenergy.

High-titer lactic acid production from pilot-scale pretreated non-detoxified rice straw hydrolysate at high-solid loading

Lignocellulosic biomasses are promising feedstocks for the production of high-value chemicals because they are abundant, inexpensive, renewable, sustainable, environmentally friendly, and can potentially reduce pollution. Furthermore, lignocellulose biomass is non-edible and a source of fermentable sugars, which makes it ideal for the fermentation of various biochemicals, such as bio-based lactic acid (LA). Furthermore, it contributes to the economic sustainability of biorefineries. LA is an industrially significant product with a large and rapidly growing market due to its attractive features and benefits. The current study demonstrates high-titer lactic acid (LA) fermentation from pretreated rice straw using co-fermenting (C5 & C6 sugars) Lactobacillus lactis 2369. Rice straw (RS) was chemically pretreated with mild acid additive in a pilot-scale (250 Kg day–1) steam-explosion unit. At first, the crude dilute acid pretreated slurry was enzymatically hydrolyzed using commercial cellulases (1.5–10 FPUg−1 residue) at 50 °C for 48 h followed by LA production for 96–140 h. In the current study high titer, LA production (82.2 gL−1) as well as higher conversion yield (87.2%) with the productivity of 0.61 gL−1h−1 were obtained with high substrate solid loading (20% wv−1) and low enzyme dose (5 FPU g−1) at 42 °C.

Towards sustainable production of bio-based lactic acid via a bio-based technical route: Recent developments and the use of palm kernel cakes in the bioconversion

The continued reliance on non-renewable fossil resources has led to serious environmental issues. In light of these concerns, the transition from non-renewable sources to more sustainable ones have been explored, as exemplified by the production of bio-based lactic acid via lignocellulosic biomass bio-refinery process. Malaysia, the second-largest producer of palm oil in the world, generates abundant, cheap, and underutilized oil palm biomass in the form of palm kernel cakes. Comprised of 50% fermentable hexose sugars, palm kernel cakes have emerged as an interesting feedstock substitute in the production of bio-based fine chemicals, e.g., lactic acid. This paper focuses on current work based on selected literature published in the 21st century on the exploitation of palm kernel cakes as a novel feedstock in bio-refinery processes after addressing the current global demand and potential commodity applications of bio-based lactic acid. It then discusses current research on potential lactic acid-producing microorganisms, with particular attention to bacteria, and different pretreatment methods for carbohydrate recovery from palm kernel cakes. It also highlights the potential of oil palm biomass, especially palm kernel cakes, as a promising commodity that contributes to sugar platforms in value-added products, e.g., biofuel, bioenergy, ethanol, acids, and fine chemicals.

Use of Corn-Steep Water Effluent as a Promising Substrate for Lactic Acid Production by Enterococcus faecium Strain WH51-1

Various challenges facing the industrial production of bio-based lactic acid (LA) such as cost of raw materials and nitrogen sources, as well as contamination risk by mesophilic and neutrophilic producers, should be overcome for the commercial production. This study aimed to investigate the feasibility of corn steep water (CSW) as a raw material for LA production using a newly thermo-alkali-tolerant lactic acid bacterium. The physicochemical characteristics of CSW were investigated. The high carbohydrates, proteins, amino acids, vitamins, essential elements, minerals, and non-protein nitrogenous compounds content confirmed that the CSW is a promising substrate for LA production. Out of 67 bacterial isolates, Enterococcus faecium WH51-1 was selected based on its tolerance to high temperatures and inhibitory compounds (sodium metabisulfate, sodium chloride, sodium acetate, and formic acid). Fermentation factors including sugar concentration, temperature, inoculum size, and neutralizing agents were optimized for LA production. Lactic acid concentration of about 44.6 g/L with a high yield (0.89 ± 0.02 g/g) was obtained using 60 g/L of CSW sugar, inoculum size 10% (v/v), 45 °C, and sodium hydroxide or calcium carbonate as a neutralizing agent. These results demonstrated the potential of strain WH51-1 for LA production using CSW effluent as raw material.

Controllable preparation and performance of bio-based poly(lactic acid-iminodiacetic acid) as sustained-release Pb2+ chelating agent

SummaryThe bio-based lactic acid (LA) and the common metal ion chelating agent iminodiacetic acid (IDA) are used to design and prepare a polymeric sustained-release Pb2+ chelating agent by a brief one-step reaction. After the analysis on theoretical calculation for this reaction, poly(lactic acid-iminodiacetic acid) [P(LA-co-IDA)] with different monomer molar feed ratios is synthesized via direct melt polycondensation. P(LA-co-IDA) mainly has star-shaped structure, and some of them have two-core or three-core structure. Thus, a possible mechanism of the polymerization is proposed. The degradation rate of P(LA-co-IDA)s can reach 70% in 4 weeks. The change of IDA release rate is consistent with the trend of the degradation rate, and the good Pb2+ chelating performance is confirmed. P(LA-co-IDA) is expected to be developed as a lead poisoning treatment drug or Pb2+ adsorbent in the environment with long-lasting effect, and this research provides a new strategy for the development of such drugs.

Expeditious production of concentrated glucose-rich hydrolysate from sugarcane bagasse and its fermentation to lactic acid with high productivity

Sugarcane bagasse (SCB) is anticipated to emerge as a potential threat to waste management in India on account of cheap surplus energy options and lower incentives through its co-generation. Through biotechnological intervention, the efficient utilization of SCB is seen as an opportunity. The present study aimed towards expeditious production of concentrated glucose-rich hydrolysate from SCB. Alkali pretreated biomass was chosen for hydrolysis with a new generation cellulase cocktail, Cellic CTec2 dosed at 25 mg g−1 glucan content. A two-step (9% + 9%) substrate feeding strategy was adopted with a gap of an hour, and saccharification was terminated in three different ways. Irrespective of the methods employed for termination, ∼84.5% cellulose was hydrolyzed releasing ≥100 g L−1 glucose from 18% biomass. Direct use of glucose-rich filtrates yielded 69.2 ± 2.5 g L−1 of L (+) lactic acid using thermophilic Bacillus coagulans NCIM 5648. The best-attained glucose and lactic acid productivities during separate hydrolysis and fermentation (SHF) in the present study were 5.27 and 2.88 g L−1 h−1, respectively. A green and sustainable process is demonstrated for the production of industrially relevant sugars from SCB at high productivity and its valorization to bio-based lactic acid.

Screening of lactic acid bacteria stable in ionic liquids and lignocellulosic by-products for bio-based lactic acid production

Lignocellulosic biomass are promising renewable resources for production of biofuels and platform chemicals. The present study encompasses the screening and isolation of lactic acid bacteria (LAB), stable in the presence of ionic liquids ([EMIM][OAc], [BMIM][MeSO4], and [BMIM][Cl]) and lignocellulosic inhibitors (HMF and furfural), and explores them for effective bio-based lactic acid production. Nineteen LAB producing isolates were identified based on their morphological, biochemical and 16S rRNA sequence analysis. Among these five LAB strains namely P. pentosaceus SKL-7, L. fallax SKL-15, L. plantarum SKL-19, L. paracasei SKL-21, and L. plantarum SKL-22 grew well in presence of ILs [EMIM][OAc], [BMIM][MeSO4], and [BMIM][Cl]. The L. plantarum SKL-22 exhibited relatively high tolerance with highest specific growth rates in presence of 0.5% and 1% [BMIM][MeSO4] and [BMIM][Cl]. Overall, L. plantarum SKL-22 produced reasonable good amount of lactic acid 34.26 g/l. It appears a promising strain for one-pot production of lactic acid from lignocellulosic biomass.

Efficient synthesis, characterization, and application of biobased scab-bionic hemostatic polymers

Under optimized reaction conditions, by directly using the hemostatic drugs 4-aminomethylbenzoic acid (ABA) and tranexamic acid (TA) as separate comonomers of lactic acid (LA), a series of copolymers, P(LA-co-ABA) and P(LA-co-TA), respectively, with different molar feed ratios were designed and synthesized via melt polycondensation and used as biobased polymeric sustained-release hemostatic materials. Their structure, properties and morphology were systematically investigated by Fourier transform infrared spectrometer (FTIR), proton nuclear magnetic resonance (1H NMR), gel permeation chromatography (GPC), X-ray diffraction (XRD), differential scanning calorimetery (DSC), thermogravimetric (TG), scanning electron microscopy (SEM), water contact angle and degradation tests. The degradation rate within 7 weeks can reach 77%. When the molar feed ratios of ABA and TA are 20% and 10%, respectively, the corresponding copolymers have relatively lower crystallinity and smaller water contact angle and exhibit the best coagulation performance. In addition, these powdery copolymers have good application convenience, can form a degradable protective membrane similar to a blood scab on the wound surface and continuously exert hemostatic effects to promote wound healing, as anticipated. A series of polymeric hemostatic materials are prepared in one-step, by using biobased lactic acid monomers and mature hemostatic drugs (4-aminomethylbenzoic acid or tranexamic acid) through direct melt polycondensation. These materials are powdery with rough and irregular surfaces, and the powder particle size is ~8–30 μm, which is beneficial to the application, immediate hemostasis and scab-bionic membrane forming. Moreover, after the degradation of these materials at 37 °C, more monomers will be released, resulting in a higher efficiency and long-term hemostatic function.

Techno-Economic Analysis of Bio-Based Lactic Acid Production Utilizing Corn Grain as Feedstock

Lactic acid is an important chemical with numerous commercial applications that can be fermentatively produced from biological feedstocks. Producing lactic acid from corn grain could complement the use of already existing infrastructure for corn grain-based ethanol production with a higher value product. The objective of this study was to evaluate the techno-economic feasibility of producing 100,000 metric tons (t) of lactic acid annually from corn grain in a biorefinery. The study estimated the resources (equipment, raw materials, energy, and labor) requirements and costs to produce lactic acid from bacteria, fungi and yeast-based fermentation pathways. Lactic acid production costs were $1181, $1251 and $844, for bacteria, fungi and yeast, respectively. Genetically engineered yeast strains capable of producing lactic acid at low pH support significantly cheaper processes because they do not require simultaneous neutralization and recovery of lactic acid, resulting in lower requirements for chemical, equipment, and utilities. Lactic acid production costs were highly sensitive to sugar-to-lactic-acid conversion rates, grain price, plant size, annual operation hours, and potential use of gypsum. Improvements in process efficiencies and lower equipment and chemical costs would further reduce the cost of lactic acid production from corn grain.

Effective biorefinery approach for lactic acid production based on co-fermentation of mixed organic wastes by Enterococcus durans BP130

Abstract Various challenges facing the industrial manufacture of biobased lactic acid (LA) have been occurred. These include substrate and/or pre-treatments cost, medium cost, and contamination risk as a result of utilizing neutral pH and mesophilic conditions. Therefore, this study focused on development of consolidated bioprocess for LA production from organic wastes under harsh conditions. A newly isolated thermo-alkali-tolerant lactic acid bacterium, Enterococcus durans BP130, was firstly used for direct LA production from banana peels (BP). Increasing the solid concentration of BP from 4.0% to 6.7% [w-dry matter/v] have resulted in increased fermentation efficiency with the highest LA production (19.2 g L−1) at 6.7% [w-dry matter/v]. Besides, co-fermentation of BP and food waste (FW) materials resulted in 13% improvements in LA concentration and 12% in LA productivity at 0.5:1 of FW:BP (w/w). Increasing of food waste concentrations could replace the nutritional components of the media and achieved increased LA production. Without any nutrients supplementation, food waste substituted the medium components and resulted in 14.3 g L−1 of LA produced using mixed substrates of FW:BP at 3:1 (w/w). The highest LA concentration of 28.8 g L−1 with a yield of 0.85 g g−1-consumed sugar and productivity of 0.24 g L−1 h−1 was achieved in batch fermentation using CaCO3 as a neutralizing agent. This study introduced effective mixed waste-based biorefinery process for direct LA production in an inexpensive fermentation system.

Efficient Conversion of Bio‐Lactic Acid to 2,3‐Pentanedione on Cesium‐Doped Hydroxyapatite Catalysts with Balanced Acid–Base Sites

AbstractWe report the design and synthesis of cesium‐doped hydroxyapatite for direct and high‐yield conversion of biobased lactic acid to 2,3‐pentanedione (72.3 %). Cs species derived from CsNO3 at high temperature of calcination is introduced into the hydroxyapatite structure to regulate its acid–base properties. It is found that a balance of acid–base chemistry favors the condensation of lactic acid to 2,3‐pentanedione. As a result, the undesired reactions such as lactic acid dehydration, decarbonylation, and coking are suppressed. Instead, a concerted catalysis between surface basic site and acidic site for lactic acid condensation to 2,3‐pentanedione dominates on the cesium‐doped hydroxyapatite catalyst, leading to a highly selective process for direct conversion of bio‐lactic acid to 2,3‐pentanedione.

Environmental impacts of producing bioethanol and biobased lactic acid from standalone and integrated biorefineries using a consequential and an attributional life cycle assessment approach

This study evaluates the environmental impacts of biorefinery products using consequential (CLCA) and attributional (ALCA) life cycle assessment (LCA) approaches. Within ALCA, economic allocation method was used to distribute impacts among the main products and the coproducts, whereas within the CLCA system expansion was adopted to avoid allocation. The study seeks to answer the questions (i) what is the environmental impacts of process integration?, and (ii) do CLCA and ALCA lead to different conclusions when applied to biorefinery?. Three biorefinery systems were evaluated and compared: a standalone system producing bioethanol from winter wheat-straw (system A), a standalone system producing biobased lactic acid from alfalfa (system B), and an integrated biorefinery system (system C) combining the two standalone systems and producing both bioethanol and lactic acid. The synergy of the integration was the exchange of useful energy necessary for biomass processing in the two standalone systems. The systems were compared against a common reference flow: “1MJEtOH+1kgLA”, which was set on the basis of products delivered by the system C. Function of the reference flow was to provide service of both fuel (bioethanol) at 99.9% concentration (wt. basis) and biochemical (biobased lactic acid) in food industries at 90% purity; both products delivered at biorefinery gate. The environmental impacts of interest were global warming potential (GWP100), eutrophication potential (EP), non-renewable energy (NRE) use and the agricultural land occupation (ALO). Regardless of the LCA approach adopted, system C performed better in most of the impact categories than both standalone systems. The process wise contribution to the obtained environmental impacts also showed similar impact pattern in both approaches. The study also highlighted that the recirculation of intermediate materials, e.g. C5 sugar to boost bioethanol yield and that the use of residual streams in the energy conversion were beneficial for optimizing the system performance.

Green metrics for sustainability of biobased lactic acid from starchy biomass vs chemical synthesis

The interest in the biotechnological production of lactic acid has increased due to the prospects of environmental friendliness and of using renewable resources instead of petrochemicals. Besides, this type of lactic acid is important for polylactic acid (PLA) production, as it is not toxic as packaging in food application while monomers of many fossil polymers are. However, lack of information can be found about the efficiency of fermentative production of lactic acid from biomass in compare with its production in a chemical way.The present paper reviews some of our recent studies concerning metrics relevant to the development of a cost-effective and sustainable viable processes for lactic acid production. In particular, the following metrics were taken for consideration: (i) material efficiency; (ii) total energy efficiency, (iii) economic added value and (iv) land use.Higher economical effect has been found by using biological conversion of wheat biomass to lactic acid vs chemical synthesis by increasing the energy efficiency by 47% and decreasing the total costs by 17%. Chemical synthesis from petrochemical resources always results in a racemic mixture of d/l-lactic acid, which is a major disadvantage of this approach, while fermentation-derived lactic acid mixtures of poly d(−) and poly l(+) give the high crystalline melting point (Tm), which is a very important criteria for improving PLA applicability for bioplastics production. Conversely, microbial lactic acid fermentation offers an advantage in terms of utilization of renewable carbohydrate biomass, low production temperature, low energy consumption, and the production of optically high pure lactic acid by selecting an appropriate strain.

Racemization-free Monomer: α-Hydroxyisobutyric Acid from Bio-based Lactic Acid

Abstract In order to solve the important problem of the racemization of poly(l-lactic acid), a high yield of racemization-free monomer: a-hydroxyisobutyric acid (HIBA) was synthesized from bio-based lactic acid by methylation using specific bases with bulky side groups. Obtained HIBA can be converted into poly(tetramethylglycolide), which is racemization-free and has higher melting and glass transition points than poly(l-lactic acid).