Local Sources of Protein in Low- and Middle-Income Countries: How to Improve the Protein Quality?

Protein inadequacy is a major contributor to nutritional deficiencies and adverse health outcomes of populations in low- and middle-income countries (LMICs). People in LMICs often consume a diet predominantly based on staple crops, such as cereals or starches, and derive most of their daily protein intakes from these sources. However, plant-based sources of protein often contain low levels of indispensable amino acids (IAAs). Inadequate intake of IAA in comparison with daily requirements is a limiting factor that results in protein deficiency, consequently in the long-term stunting and wasting. In addition, plant-based sources contain factors such as antinutrients that can diminish protein digestion and absorption. This review describes factors that affect protein quality, reviews dietary patterns of populations in LMICs and discusses traditional and novel small- and large-scale techniques that can improve the quality of plant protein sources for enhanced protein bioavailability and digestibility as an approach to tackle malnutrition in LMICs. The more accessible small-scale food-processing techniques that can be implemented at home in LMICs include soaking, cooking, and germination, whereas many large-scale techniques must be implemented on an industrial level such as autoclaving and extrusion. Limitations and considerations to implement those techniques locally in LMICs are discussed. For instance, at-home processing techniques can cause loss of nutrients and contamination, whereas limitations with larger scale techniques include high energy requirements, costs, and safety considerations. This review suggests that combining these small- and large-scale approaches could improve the quality of local sources of proteins, and thereby address adverse health outcomes, particularly in vulnerable population groups such as children, adolescents, elderly, and pregnant and lactating women.

Secretion-Catalyzed Assembly of Protein Biomaterials on a Bacterial Membrane Surface.

Protein-based biomaterials have played a key role in tissue engineering, and additional exciting applications as self-healing materials and sustainable polymers are emerging. Over the past few decades, recombinant expression and production of various fibrous proteins from microbes have been demonstrated; however, the resulting proteins typically must then be purified and processed by humans to form usable fibers and materials. Here, we show that the Gram-positive bacterium Bacillus subtilis can be programmed to secrete silk through its translocon via an orthogonal signal peptide/peptidase pair. Surprisingly, we discover that this translocation mechanism drives the silk proteins to assemble into fibers spontaneously on the cell surface, in a process we call secretion-catalyzed assembly (SCA). Secreted silk fibers form self-healing hydrogels with minimal processing. Alternatively, the fibers retained on the membrane provide a facile route to create engineered living materials from Bacillus cells. This work provides a blueprint to achieve autonomous assembly of protein biomaterials in useful morphologies directly from microbial factories.