Isolation and Characterization of Beneficial Bacteria from Food Process Wastes

Deeper insight into the storage time of food waste on black soldier fly larvae growth and nutritive value: Interactions of substrate and gut microorganisms

Biological treatment of food waste (FW) by black soldier fly larvae (BSFL) is considered as an effective management strategy. The composition and concentrations of nutrients in FW change during its storage and transport period, which potentially affect the FW conversion and BSFL growth. The present study systematically investigated the effect of different storage times (i.e., 0-15 d) on FW characteristics and its substantial influence on the BSFL growth. Results showed that the highest larvae weight of 282 mg and the shortest growth time of 14 days were achieved at the group of FW stored for 15 days, but shorter storage time (i.e., 2-7 d) had adverse effect on BSFL growth. Short storage time (i.e., 2-4 d) improved protein content of BSFL biomass and prolonged storage time (i.e., 7-10 d) led to the accumulation of fat content. The changes of substrate characteristics and indigenous microorganisms via FW storage time were the main reasons for BSFL growth difference. Lactic acid (LA) accumulation (i.e., 19.84 g/L) in FW storage for 7 days significantly limited the BSFL growth, leading to lowest larvae weight. Both the substrate and BSFL gut contained same bacterial communities (e.g., Klebsiella and Proteus), which exhibited similar change trend with the prolonged storage time. The transfer of Clostridioides from substrate to BSFL gut promoted nutrients digestion and intestinal flora balance with the FW stored for 15 days. Pathogens (e.g., Acinetobacter) in BSFL gut feeding with FW storage time of 7 days led to the decreased digestive function, consistent with the lowest larvae weight. Overall, shorter storage time (i.e., 2-7 d) inhibited the BSFL digestive function and growth performance, while the balance of the substrate nutrients and intestinal flora promoted the BSFL growth when using the FW stored for 15 days.

Food waste-based bio-fertilizers production by bio-based fermenters and their potential impact on the environment

Increasing food waste is creating a global waste (and management) crisis. Globally, ∼1.6 billion tons of food is wasted annually, worth ∼$1.2 trillion. By reducing this waste or by turning it into valuable products, numerous economic advantages can be realized, including improved food security, lower production costs, biodegradable products, environmental sustainability, and cleaner solutions to the growing world's waste and garbage management. The appropriate handling of these detrimental materials can significantly reduce the risks to human health. Food waste is available in biodegradable forms and, with the potential to speed up microbial metabolism effectively, has immense potential in improving bio-based fertilizer generation. Synthetic inorganic fertilizers severely affect human health, the environment, and soil fertility, thus requiring immediate consideration. To address these problems, agricultural farming is moving towards manufacturing bio-based fertilizers via utilizing natural bioresources. Food waste-based bio-fertilizers could help increase yields, nutrients, and organic matter and mitigate synthetic fertilizers' adverse effects. These are presented and discussed in the review.

Isolation, characterization, identification, genomics and analyses of bioaccumulation and biosorption potential of two arsenic-resistant bacteria obtained from natural environments

Arsenic (As) is a significant contaminant whose unrestrained entrance into different ecosystems has created global concern. At the cellular level, As forms unsteady intermediates with genetic materials and perturbs different metabolic processes and proper folding of proteins. This study was the first in this region to explore, isolate, screen systematically, and intensively characterize potent As-tolerant bacterial strains from natural environments near Raiganj town of Uttar Dinajpur, West Bengal. In this study, two potent Gram-negative bacterial strains with high tolerance to the poisonous form of As, i.e., As(III) and As(V), were obtained. Both the isolates were identified using biochemical tests and 16S rRNA gene sequencing. These bacteria oxidized toxic As(III) into less poisonous As(V) and depicted tolerance towards other heavy metals. Comparative metabolic profiling of the isolates in control and As-exposed conditions through Fourier-transform infrared spectroscopy showed metabolic adjustments to cope with As toxicity. The metal removal efficiency of the isolates at different pH showed that one of the isolates, KG1D, could remove As efficiently irrespective of changes in the media pH. In contrast, the efficiency of metal removal by PF14 was largely pH-dependent. The cell mass of both the isolates was also found to favourably adsorb As(III). Whole genome sequence analysis of the isolates depicted the presence of the arsRBC genes of the arsenic operon conferring resistance to As. Owing to their As(III) oxidizing potential, high As bioaccumulation, and tolerance to other heavy metals, these bacteria could be used to bioremediate and reclaim As-contaminated sites.

A high-yielding strain of indole-3-acetic acid isolated from food waste compost: metabolic pathways, optimization of fermentation conditions, and application

Food waste is a potential resource to prepare microbial fertilizer. However, functional microorganisms derived from the food waste compost (FWC) are relatively lacking. We have isolated, identified, characterized and optimized a high-yielding indole-3-acetic acid (IAA) strain from FWC and further evaluated its growth promoting effect on plants. A IAA high-yielding strain, Providencia sp.Y, with an initial IAA yield of 139.98 mg L-1, was obtained through high-throughput screening, and identified by 16S rRNA gene sequence. The novel strain Y may simultaneously involve the following three pathways from L-tryptophan to IAA, which were identified using liquid chromatography-tandem mass spectrometry: (1) L-tryptophan-indole-3-ethanol-indole-3-acetaldehyde-indole-3-acetic acid; (2) L-tryptophan-1-hydroxy-indole-3-ethanol-indole-3-acetic acid; (3) L-tryptophan-indole-3-acetamide-indole-3-acetic acid. The most suitable comprehensive conditions for IAA production, which were optimized by single factor experiment, were: culture time 12 h, inoculation amount 2% (v/v), NaCl concentration 4% (w/v), culture temperature 25℃, initial pH = 5, and L-tryptophan concentration 3.0 g L-1. The yield of IAA after optimization was increased by 590.48%, from 139.98 mg L-1 (before optimization) to 966.54 mg L-1. Diluted 200-fold microbial suspension could significantly improve the growth of pakchoi seedlings. The seedling plant height, root length, leaf width, leaf length, and fresh weight with microbial suspension increased by 17.39%, 107.35%, 77.98%, 37.75%, and 215.38%, respectively, compared with those without microbial suspension. The increase was greater than that of commercial bacterial agents. In conclusion, this isolated strain can be used as an economical microbial inoculant and provides a new germplasm resource for developing microbial fertilizers.

Diversity and enzymatic activity of the microbiota isolated from compost based on restaurant waste and yard trimmings

Introduction

The bad management of organic waste negatively affects environmental quality and composting has been a viable recycling alternative. Microorganisms are responsible for waste degradation during the composting process and, consequently, for transforming this waste into natural fertilizer. This work aimed to analyze and identify the biodiversity of yeasts and filamentous fungi throughout a composting process based on organic residues under different treatments (commercial inoculum, non-commercial inoculum, and control treatment) and to investigate the enzymatic activity of these microorganisms.

Methods

Microorganisms were isolated and identified from samples at 0, 5, 10, 20, 40, 60, and 120 days. Filamentous fungi were identified according to their macroscopic and microscopic characteristics, and yeasts were identified by sequencing the 18S rDNA region. All identified strains were evaluated for ligninolytic, cellulolytic, hemicellulolytic, amylolytic, pectinolytic, proteolytic, lipolytic, and ammonification. During the composting phases, the filamentous fungi were higher than the yeast population.

Results and discussion

At the beginning of the process, a higher species diversity was observed, and the population of yeasts and filamentous fungi was, on average, 6.50 log CFU g−1. The microbial communities were similar throughout the process in the two inoculated treatments, which showed more significant microbial activity, diversity, and efficiency in the transformation of organic matter, and consequently, advantages in terms of the final product quality compared to the control treatment. The yeasts Pichia kudriavzevii, Pichia farinosa, Issatchenkia orientalis, and the filamentous fungi of the genus Aspergillus spp. proved to have high biotechnological value and could be used as starter cultures to accelerate the composting process.

An Assessment of the Lactic Acid-Producing Potential of Bacterial Strains Isolated from Food Waste

Lactic acid (LA) is widely used in many industries as a crucial starting material in food products, bio-based materials, and biodegradable polymers. The goals of this research were to isolate LA bacteria from food wastes, assess their potential for LA production, and study their growth characteristics. In this study, six bacterial strains were isolated from food waste and identified using 16S rRNA gene sequencing; namely, Weissella viridescens WJ39, Leuconostoc lactis YS33, Leuconostoc citreum KD42, Leuconostoc mesenteroides VN60, Macrococcus caseolyticus FCI29, and Weissella confusa RG41. W. viridescens WJ39 showed the highest potential for lactic acid production (17.56 g L−1day−1), and the lowest potential was found in L. lactis YS33 (14.09 g L−1day−1). There were significant differences (p < 0.05) in the LA production rates among Weissella spp., Leuconostoc spp., and Macrococcus spp. Moreover, dramatic differences in growth rate were observed among the six strains. W. viridescens WJ39 exhibited the highest growth rate (0.80 h−1), while M. caseolyticus FCI29 exhibited the lowest growth rate (0.57 h−1). W. viridescens WJ39 also exhibited lactic acid production (at a rate around 2 g L−1day−1) in a lab incubation experiment with food waste as a nutrient source. The draft genome of W. viridescens WJ39 with 16 contigs was constructed with an N50 of 215217 bp. The genome size was approximately 1.54 Mb, with a GC content of 41%. A hicD gene, known to catalyze the conversion of pyruvate to D-lactate, was discovered in the genome. This study illustrated the potential for the production of lactic acid from food waste with lactic acid bacteria.