Lactic acid fermentation within a cascading approach for biowaste treatment

A state-of-the-art review of biowaste biorefinery

Biorefineries provide a platform for different industries to produce multiple bio-products enhancing the economic value of the system. The production of these biorefineries has led to an increase in the generation of biowaste. To minimize the risk of environmental pollution, numerous studies have focused on a variety of strategies to mitigate these concerns reflected in the vast amount of literature written on this topic. This paper aims to systematically analyze and review the enormous body of scientific literature in the biowaste and biorefinery field for establishing an understanding and providing a direction for future works. A bibliometric analysis is first performed using the CorTexT Manager platform on a corpus of 1488 articles written on the topic of biowaste. Popular and emerging topics are determined using a terms extraction algorithm. A contingency matrix is then created to study the correlation of scientific journals and key topics from this field. Then, the connection and evolution of these terms were analyzed using network mapping, to determine relationships among key terms and analyze notable trends in this research field. Finally, a critical review of articles was presented across three main categories of biowaste management such as mitigation, sustainable utilization, and cleaner disposal from the perspective of the biorefinery concept. Operational and technological challenges are identified for the integration of anaerobic digestion in biorefineries, especially in developing nations. Moreover, logistical challenges in the biorefinery supply-chain are established based on the economics and collection aspect of handling biowaste.

Formulation of a fermentation substrate from pineapple and sacha inchi wastes to grow Weissella cibaria

Gold honey variety pineapple wastes and sacha inchi sub-products (SIS) were characterized in their elemental, physical, and chemical form in order to formulate a supplemented fermentation substrate (SFS) for the growth Weissella cibaria. The peels and fresh cores of the pineapple (FPP, FPC) were dried and ground (PPP, PPC) and then mixed (MCPP). The following procedures were then undertaken: a physicochemical characterization (moisture, a_w, pH, acidity, and soluble solids) of the SIS, FPP, FPC, PPP, and PPC; a proximal characterization of he FPP, FPC, SIS, and SFS; and an elemental analysis (C-N₂-H₂-O₂-S) of the MCPP, SIS, and W. cibaria, which allowed the stoichiometric equation to be defined and the SFS to be formulated. We then evaluated the effect that homogenization and heating to boiling point had on the concentration of reducing sugars in the SFS (g L^-1). Finally, W. cibaria´s kinetic fermentation parameters were evaluated in the SFS and in a commercial substrate (control). The results showed FPP and FPC yields of 26.02 ± 0.58 and 14.69 ± 1.13%, respectively; a higher total sugar content in FPC (7.21%) than in FPP (6.65%); a high crude protein content in SIS (56.70%), and a C:N₂ ratio of 6.50:1.00. Moreover, the highest concentration of reducing sugars (4.44 ± 0.29 g L^-1) in the SFS was obtained with 5 h of hydrolysis under homogenization pre-treatments and heating until boiling. The SFS allowed the adaptation of W. cibaria, and there was a biomass production of 2.93 g L^-1 and a viability of 9.88 log CFU mL^-1. The formulation of an unconventional fermentation substrate from -Agro-industrial wastes of pineapple and sacha inchi to produce valuable products (such as lactic acid biomass through fermentation), is an excellent perspective for large-scale application.

Microbiome sharing between children, livestock and household surfaces in western Kenya

The gut microbiome community structure and development are associated with several health outcomes in young children. To determine the household influences of gut microbiome structure, we assessed microbial sharing within households in western Kenya by sequencing 16S rRNA libraries of fecal samples from children and cattle, cloacal swabs from chickens, and swabs of household surfaces. Among the 156 households studied, children within the same household significantly shared their gut microbiome with each other, although we did not find significant sharing of gut microbiome across host species or household surfaces. Higher gut microbiome diversity among children was associated with lower wealth status and involvement in livestock feeding chores. Although more research is necessary to identify further drivers of microbiota development, these results suggest that the household should be considered as a unit. Livestock activities, health and microbiome perturbations among an individual child may have implications for other children in the household.

Novel pH control strategy for efficient production of optically active l-lactic acid from kitchen refuse using a mixed culture system

Uninvestigated control factors of meta-fermentation, the fermentative production of pure chemicals and fuels in a mixed culture system, were examined for production of optically pure l-lactic acid (LA) from food waste. In meta-fermentations by pH swing control, l-LA production with 100% optical purity (OPl-LA) was achieved even using unsterilized model kitchen refuse medium with preferential proliferation of l-LA-producing Bacillus coagulans, a minor member in the seed, whereas agitation decreased OPl-LA drastically. pH constant control shortened the fermentation time but decreased OPl-LA and LA selectivity (SLA) by stimulating growth of heterofermentative Bacillus thermoamylovorans. Deliberately switching from pH swing control to constant control exhibited the best performance for l-LA production: maximum accumulation, 39.2gL(-1); OPl-LA, 100%; SLA, 96.6%; productivity, 1.09gL(-1)h(-1). These results present a novel pH control strategy for efficient l-LA production in meta-fermentation based on a concept different from that of pure culture systems.

Probiotics production and alternative encapsulation methodologies to improve their viabilities under adverse environmental conditions

Probiotic products are dietary supplements containing live microorganisms producing beneficial health effects on the host by improving intestinal balance and nutrient absorption. Among probiotic microorganisms, those classified as lactic acid bacteria are of major importance to the food and feed industries. Probiotic cells can be produced using alternative carbon and nitrogen sources, such as agroindustrial residues, at the same time contributing to reduce process costs. On the other hand, the survival of probiotic cells in formulated food products, as well as in the host gut, is an essential nutritional aspect concerning health benefits. Therefore, several cell microencapsulation techniques have been investigated as a way to improve cell viability and survival under adverse environmental conditions, such as the gastrointestinal milieu of hosts. In this review, different aspects of probiotic cells and technologies of their related products are discussed, including formulation of culture media, and aspects of cell microencapsulation techniques required to improve their survival in the host.

Treatability of cheese whey for single-cell protein production in nonsterile systems: Part I. Optimal condition for lactic acid fermentation using a microaerobic sequencing batch reactor (microaerobic SBR) with immobilized Lactobacillus plantarum TISTR 2265 and microbial communities

Cheese whey contains a high organic content and causes serious problems if it is released into the environment when untreated. This study aimed to investigate the optimum condition of lactic acid production using the microaerobic sequencing batch reactor (microaerobic SBR) in a nonsterile system. The high production of lactic acid was achieved by immobilized Lactobacillus plantarum TISTR 2265 to generate an acidic pH condition below 4.5 and then to support single-cell protein (SCP) production in the second aerobic sequencing batch reactor (aerobic SBR). A hydraulic retention time (HRT) of 4 days and a whey concentration of 80% feeding gave a high lactic acid yield of 12.58 g/L, chemical oxygen demand (COD) removal of 62.38%, and lactose utilization of 61.54%. The microbial communities in the nonsterile system were dominated by members of lactic acid bacteria, and it was shown that the inoculum remained in the system up to 330 days.

End-product inhibition and acidification limit biowaste fermentation efficiency

Converting waste to resource may mitigate environmental pollution and global resource limitation. The platform chemical lactic acid can be produced from biowaste and its liquid fraction after solid-liquid separation. A fermentation step for lactic acid production prior to the conversion of biowaste to methane and organic fertilizer would increase the biowaste's value. Despite the huge potential and promising results of the treatment procedure, the reasons for efficiency loss observed previously need to be addressed in order to pave the way for an up-scaling of the fermentation process. Therefore, biowaste was fermented applying pH control, acid extraction and glucose addition in order to counteract reasons such as acidification, end-product inhibition and carbon limitation, respectively. The fermentation was competitive compared to other renewable lactic acid production substrates and reached a maximum productivity of >5 g Clactic acidg(-1)Ch(-1) and a concentration exceeding 30 g L(-1). A combination of acidification and end-product inhibition was identified as major obstacle. Lactobacillus crispatus and its closest relatives were identified as key lactic acid producers within the process using Miseq Illumina sequencing.