Chapter 3 - Soil microbes as biopolymers to enhance soil mechanical properties: a sustainable approach

Abstract

Indiscriminate use of natural resources in all walks of life to satisfy human needs has caused us to rethink our future survival. Several times, “war for water” has been aired on Blue Planet Earth, where 71% water is found, while much less discussion has been made of the 29% land mass. Earth's land surface (29%) is divided into 70% habitable land, 10% glaciers, and 19% barren land. Agricultural activities are performed on 50% (54million km2) of total habitable land (104million km2). These data signify the importance of conserving this natural resource in a holistic way for upcoming generations. Synthesizing and using microbe-derived biopolymers is the sharp shining light in the darkness of capitalistic modernization. Agricultural activities like deep summer ploughing, tillage operations, crop rotation, land fallowing, etc. have been performed since ancient times to build up the functionally active microbiome to strengthen soil properties. Using soil microbial metabolites (also called biopolymers) for soil amelioration after implementing modern agriculture acts as a supporting tool for sustainable agriculture. Chitosan, xanthan, cellulose, dextrin, silk fibroin, and other well-documented biopolymers are obtained from soil-resident fungi, bacteria, archaea, and algae, as well as from silkworm insects. Chitosans and dextrins are used as seed coating materials to immobilize microbial metabolites and make the soil suppressive. Levans are carbon compounds secreted by both plans and fungi that regulate soil stability by binding various ions. Moreover, silk fibroins and trehalose provide the strength to the soil to bear biotic and abiotic stresses. These biopolymeric substances also confer on microorganisms the ability to overcome stressful environments such as those characterized by drought, pesticides, etc. They stabilize soil and regulate nutrients and water flow across plant roots through biofilm formation that indirectly enhances crop productivity.